Tonight's Reported Missing on BBC One (September 2) followed the search for two homeless men.
While most people who go missing are reported to police within a few hours, but for those who live on the streets, it isn’t always so straightforward.
The first of the night's two cases focused on 37-year-old Aaron who was reported missing by the Gloucester homeless healthcare centre.
It transpired that no one had seen him for two months as police officers started to scour the streets and homeless shelters of Gloucester but could find no trace of him.
The town’s rough sleepers said they knew him well, but no one had any idea what may have happened to him.
Aaron is known to be a class A drug user, and although he has a sister, she had struggled to help him.
As the search progressed, police tragically discovered a body in woodland - but it was not Aaron.
The body was identified to be that of another homeless person, a German woman called Ruth, who hadn't ever been reported missing.
Police were ultimately able to track Aaron down to a woman's house by tracing his cash withdrawals after he made contact with his sister via Facebook.
The second case focused on another drug user who was added to the missing persons priority list.
James, of no fixed address, discharged himself from hospital against medical advice.
Fears quickly mounted that he was at risk of overdosing or being exploited by other drug users.
Police launched an urgent search operation to try to track him down and were able to find CCTV of James with another person.
James was found by the police, who had to do their best to persuade him to return to hospital for treatment.
He ultimately returned to receive help and is now in recovery.
Reported Missing airs on BBC One on Wednesday nights at 9PM.
You can watch episodes online and catch up via the BBC iPlayer.