The complexity rests with the unknown of where the victim is, what happened to them, or why they disappeared.

But in a recent move to streamline the Missing Persons Registry, the outcome of often tragic cases has significantly turned around for the better.

Within roughly a 300km radius of Wagga, there are currently at least eight people who remain on the Missing Persons Registry, aged from as young as 15 at the time of disappearance to as old as 66.

Missing Persons Registry Commander Detective Inspector Glen Browne said the system had developed enormously over the decades.

"Back in the 1930s, we had the unit for missing persons, but it wasn't until July 1, 2019, that we developed the actual Missing Persons Registry which sits withing each State Crime Command alongside other specialist units like the Sex Crimes Squad," he said.

"Now, the matters are much more investigation-focused, and the staff are designated detectives and intelligence analysts."

The result has been life-changing, literally, for many.

Where the state once averaged about 150 long-term missing persons reported per year, that has since dropped to just 18 under the new system.

Detective Inspector Browne added that the prior average of 26 people per year who sadly never turned up had also dropped to as low as 11.

"It's incredible to see the difference the registry has made," he said.

Given the unknowns of a missing person case, Detective Inspector Browne said investigations are made all the more difficult for a number of reasons.

"You never really know if the disappearance is suspicious or not, if it may be suicide or someone choosing to not be found," he said.

"There's also always all sorts of conjecture, there's speculation from the public and the media, which can often help but also can have the opposite effect."

Detective Inspector Browne said investigating a case regionally presents its own set of challenges.

"In the cities these days, there is an abundance of CCTV footage and security cameras to assist authorities, whereas regionally, that's often not the case," he said.

"So there's definitely differences in logistics, but the mysteries are quite often very similar."

While Detective Inspector Browne said some people are "met with foul play", others "genuinely decide to start a new life".

"Since 2019 in NSW, we have located more than 50 long term missing persons who are still alive, they managed to either travel overseas, change their names, remarry and all sorts," he said.

"But then there's also the more than 130 long term missing persons who sit with the Homicide Squad and are presumed dead."

The NSW Police Force has recently launched a familial DNA collection pilot program on the state's Mid North Coast, which aims to assist detectives with ongoing historic missing persons investigations.

The collection of DNA samples is a fundamental function of missing persons, unidentified bodies and human remains investigations, and while only in the pilot phase, Detective Inspector Browne said the system will branch out to regions like the Riverina.

"It is essentially being rolled out based on statistical hot spots for missing persons, but the response so far has been extraordinary," he said.

Programs like the familial DNA collection go a long way toward solving missing persons cases, which Detective Inspector Browne said was vital to alleviate the heartache of families affected.

"I can't stress the importance of this work enough," he said.

"The toll that a longer term missing person takes on loved ones is phenomenal, and to be honest, it's just as difficult even for those missing for short time periods.

"The unit does provide support groups for friends and families of missing persons, they host regular meets and share their stories, and when you hear about these people, it really hits home just how important this work is and how vital it is to prioritise such cases."

The two biggest issues regarding missing persons in NSW are youth in out of home care, and people under the care of mental health institutions, according to Detective Inspector Browne.

"When young people in particular go missing, we know they are often engaging in all sorts of risk-taking behaviour, so one of our big focuses is on reducing that rate of going missing through youth action programs," he said.

"That subsequently reduces the rate at which they engage in those risky behaviours, and potentially, save these kids' lives."

Families and friends of missing persons in the Riverina region continue to hold out hope of finding their loved ones. These are their stories:

Last seen on November 14, 2002, in Wagga, Rafael Vanegas would now be 76 years old.

Mr Vanegas, an El Salvador refugee, was a well-known figure in Wagga's central business district where he wandered along the streets wearing a distinctive Akubra hat.

The father of eight suffered from paranoid schizophrenia, and had a fear of police from his time held captive by militia in El Salvador.

Investigators believe the 58-year-old may have entered bushland, which he often did to feel safe.

He has not made contact with friends or family, and has not been seen since.

At just 15 years old, Stuart Lamb went missing from Moama on November 28, 1996. He would now be 39 years old.

The young boy from Echuca was last seen by his friend when he jumped into the water of the Murray River.

Tragically, Mr Lamb was never seen again, and despite extensive searches underwater and along the river, his body has never been recovered.

He has not made contact with anyone or been seen since.

Wagga man Andrew Bourke was camping with his friend Wayne Candish at Brungle on July 29, 2011, by the banks of the Tumut River.

The pair had been drinking, and fell asleep in Mr Bourke's ute when it reportedly rolled into the river just after midnight.

Mr Candish was able to escape to passenger's seat and swim to shore as the vehicle sunk, but sadly, Mr Bourke was not.

Numerous police searches and rescue crews scoured the area over the years, but Mr Bourke's body was never able to be found.

The Coroner ruled it likely that Mr Bourke died from either hypothermia or drowning.

Last seen in the Lavington area on July 9, 2004, Julie Beyer was 43 years old at the time of her disappearance.

In 2012, Ms Beyer was declared deceased, with deputy state coroner Paul MacMahon saying there was no evidence she had been alive since September 10, 2004 - the last time she used her bank account.

The vehicle she was travelling in has never been found and its registration expired in 2004.

Ms Beyer spent 11 days in Nolan House at Albury Base Hospital for mental health issues before being released on July 6, 2004.

She packed her vehicle and left her Webb Street home with the intention of travelling to Mackay in Queensland.

Mr MacMahon said there were bank transactions at Dubbo and Tennant Creek early in September.

Authorities say it is likely she was driving to Katherine where her son Anthony was studying at the Charles Darwin University campus.

Disappearing at 18 years old, Niamh was last seen alive in 2002.

She had spent the summer fruit picking in Batlow and was set to meet her sister Fionnuala Hagerty in Sydney, but never made the journey.

"We knew almost immediately it wasn't going to be good news," Ms Hagerty said.

"She was meant to meet me in Sydney and we were going to go home to Armidale together to see the family for Easter.

"Everyone that had been with her leading up to that knew her plans, she was really excited to see us and also to start uni the next year."

Police were told that the Armidale teen left a campground at Jingellic on Saturday, March 30, and prior to her disappearance, had been dropped off at Gocup Road, Tumut, by an associate.

A coronial inquest in March 2012 determined Niamh had died at or near Tumut, by a person or persons unknown to her, on March 30 or 31, 2002.

Despite extensive investigations, no trace of the teenager has ever been found and no one has been charged in connection with her disappearance.

James Rice was last seen when a neighbour dropped him off near his property in Condobolin on Tuesday, July 13, 1999.

When family and friends hadn't heard from Mr Rice for an extensive period of time beyond that, being described as 'unusual' for James, alarm bells started ringing.

Mr Rice, who would now be 52 years old, has not been seen or heard from since.

Sheep farmer Ian Gray was last seen leaving his home in Bunnaloo on September 11, 2015.

He left in a vehicle with the number plate AG-46-AJ after telling his family he was "going for a drive".

While there have been several alleged sightings of Mr Gray in Victoria and NSW since he was reported missing, neither Mr Gray nor his vehicle have been found.

The farmer's disappearance has been described as "out of character" as he had a close relationship with his family.

Ruth Ridley went missing at 58 years old on October 30, 2019.

Detectives believe she was camping at Neil's Reserve on Murray River Road at Walwa on October 26 and 27.

Ms Ridley had recently separated from her husband Gary Ridley, 61, but the pair living in Tumbarumba had been recorded on security cameras, including one at an Albury supermarket, in the lead-up to camping in the Upper Murray.

Her husband's body was later found close to Pikes Dam near Shelley, and Victoria Police believe he was responsible for Ms Ridley's death.

But despite extensive searches by both Victoria and NSW police around the Corryong and Walwa areas, there's been no sign of Ms Ridley.

If you have any information that may assist police to locate these missing persons, call Crime Stoppers on 1800 333 000.