The Families and Friends of Missing Persons Unit, which is attached to the NSW Attorney-General's Department, said it had received a number of calls on Wednesday morning from families of missing persons expressing anguish over the developments in Cleveland.

Unit co-ordinator Liz Davies said families of missing persons often closely watched cases similar to their own.

"For families where a loved one is missing, particularly a young person, this is not something they hear about often," Ms Davies said. "But when they do the possibility that it may have occurred to their young person or their young child is reawakened or comes to the surface once again.

"It's a difficult combination; the hope that their loved one may still be alive but the anguish that if that is the case, why can they not make contact, why haven't they made contact and what might they be living with."

Ms Davies said the Cleveland incident was a "rarity" but for families of missing people "hope" was what motivated them and kept them going.

"Logically we can say that [Cleveland] is a rarity, but it still happened," she said. "This is why we say do not give up hope. And is there anything wrong with hanging on to some hope?"

Ms Davies said people should contact the Families and Friends of Missing Persons Unit if the Cleveland rescue had stirred up issues of distress.