Lake Illawarra police are still searching for Phillip Morgan who absconded from Shellharbour hospital late last year, his family giving a public plea for help.

The 66-year-old was detained by police on November 14 and was admitted to a psychiatric unit.

Later that day, he disappeared.

His sister, Clare Morgan, said it was not the first time he had disappeared and, due to his mental state, she had concerns for his welfare.

"We know he's alive as he's been using his bank account; it's a choice that he's made to go away from us," she said.

"It's been hard for my parents more than anything else ... we love him and hope that he's OK."

Lake Illawarra Crime Co-ordinator Senior Sergeant Matthew Brophy said Mr Morgan was likely to be in South Australia or Victoria, but missing persons cases often became difficult between states.

"The ability for us to follow it up with specific knowledge of the matter becomes difficult ... the Victorian police have got a completely different system and doesn't necessarily come up as a missing person on their system."

Senior Sergeant Brophy said if a person was detained by police in another state due to their mental health and taken for psychiatric treatment, that did not resolve the issue of them returning to their family if at legal age.

"Let's say, for instance, the police do sight this person in Victoria or in another state, and his behaviour is rational ... all we can do is say we've found him and tell the family we've found him, but if his wishes are the family not know where he is, we're not entitled to tell his family."

Thankfully for Lake Illawarra command, the majority of their missing persons were "young teenagers who are just rebelling against the house rules".

However, this isn't the case for all areas. Officers from Wollongong Local Area Command are still searching for clues as to what happened to Attila Bogar, who vanished in February this year.

The 36-year-old disappeared on Picton Road, two days after he made a peculiar overnight trip to Sydney from his Melbourne home.

His silver Audi was found abandoned about six kilometres west of Mount Ousley - his iPad, laptop and mobile phone inside. Witnesses told police the car may have been there for several days.

Meantime, the family of Mark Rowles, 58, are still at wits' end after he left the family home in Keiraville on February 8, never to return.

Anyone with information on the above cases should contact Crime Stoppers on 1800 333 000.