This teen complained of a headache and landed in hospital. Hours later she vanished - and hasn't been seen for 35 years. This is her story - and how a chilling diary entry could help solve the mystery

A woman has launched a desperate plea to bring her sister home for Christmas 35 years after she disappeared from a hospital in a small rural community. 

Thi Kim Hoa Tran suffered a migraine on August 23, 1985, and was taken to Lyell McEwin Hospital in Elizabeth, north of Adelaide, by her father. 

Kim, who was aged between 16 and 18 at the time, was quickly given a bed and her father left the hospital to pick up his other daughter from school.

Later that evening, Kim's father received a call alerting him that his daughter had been discharged and was ready to be picked up.

But the teenager was never seen again.

Thi Kim Hoa Tran was last seen in South Australia on August 23, 1985 

Kim's younger sister, who was five at the time of the disappearance, has now sought the assistance of private investigator Luke Athens to help uncover the mystery that has riddled her family for decades.

The family-of-four immigrated to Australia from Vietnam four years before Kim vanished. 

They barely spoke English and by modern standards, Kim's identity was barely documented. 

Kim's sister, who wishes to remain anonymous, recalls her father coming back from the hospital and saying Kim was 'not there and that someone had taken her'.

'They called the police, police said they couldn't do anything as she was discharged and of age,' the woman told Daily Mail Australia.  

'My parents at the time didn't speak English. They couldn't seek help.

'They didn't know who to go to.'

The disappearance has haunted Kim's sister for years and she has now decided it is time to find answers. 

'I think about my sister all the time. It's been 35 years,' she said.

Kim's father had taken her to Lyell McEwin Hospital in Elizabeth, north of Adelaide, after she suffered a migraine 

'I've gone on to have an education and a family. And I always wonder what milestones she's gone through.

'I want to find her. I want to find out happened to her.' 

The woman's parents are no longer alive.

Kim's sister said there was a 'certain element of shame' after the tragedy struck as the family had moved from Vietnam to Australia for a fresh start.   

'Throughout the years, my parents have found it very hard to talk about,' she said.

'It was something that was really painful for them. Not knowing the language at the time.

'Imagine taking your daughter to the hospital for a migraine and never seeing her again.' 

Private investigator Luke Athens has been on the case for about two-a-half-months. One woman shared a diary entry from the 1985 evening Kim disappeared

Mr Athens has been working on the investigation for about two-and-a-half months but has decided to share the case publicly in the hope he can chase further leads.

 Private investigator Luke Athens said he is 'committed' to finding answers

He has travelled to South Australia, tracking down everyone in the state with the same name - but to no avail.

'I don't feel like she's in South Australia anymore,' he said. 

Mr Athens said the case is particularly difficult as they don't know Kim's official age and her name could have changed.

'We're not 100 per cent sure this is her real name. We're just going off that Vietnamese name,' he said.

Mr Athens has interviewed neighbours who lived in the area at the time.

One woman shared a diary entry from the 1985 evening Kim disappeared.

The scribbled entry read: 'Kim. Kidnapped? Police.'

Mr Athens said there was also an unconfirmed sighting of Kim at the shops in Elizabeth in 2012.  

Kim's sister has shared a picture of herself with a glow worm toy - the one gift she received from her sister. 'My first toy, I've kept it all these years,' she said

The private investigator said he is 'committed' to finding answers. 

'If nothing comes from this release, I'll be searching every single state,' he said.

Mr Athens said his investigation has been a bit 'disappointing' so far as he doesn't think Kim's case has gotten the same amount of attention other missing people would. 

'If this for instance was a blue-eyed blonde hair western girl this s**t would be all over the media,' he said. 

'Because this is a Vietnamese immigrant, it's swept under the carpet a bit.'

Both Mr Athen's and Kim's sister think it's too soon to know what happened to the teenager.  

'I've had many thoughts over the years but conclusively I don't know what happened to her,' the woman said. 

Kim's sister said she struggles to understand how no one saw the Vietnamese teenager on the day she vanished. She had no money and no belongings with her.  

The scribbled diary entry read: 'Kim. Kidnapped? Police.'

There is a $20,000 reward for information directly leading to Kim's whereabouts.

'Through this investigation, I just hope to find her, whether she is here or not,' Kim's sister said.

'Going public with this, we're hoping that anyone with information can lead us back to that night in 1985.

'We're just imploring anyone to come forward so that my family can have some closure.

'Somebody somewhere might know something.' 

The woman has shared a picture of herself with a glow worm toy - the one gift she received from Kim.

'My first toy, I've kept it all these years,' she said. 

Anyone with information can contact Mr Athens here.