Some time between 6.30am and 9am on August 7, he wandered a short distance from his tent into dense bushland in Sydney's Hawkesbury region.

He hasn't been seen since.

On Thursday, more than a month after their son vanished, Mr Chalaer's family made a desperate plea for help.

Police wrapped up the search operation for the hotel management student and avid music lover in August and will only conduct sporadic searches in the future.

They found Mr Chalaer's shoes, with the socks tucked inside, about 400 metres from the campsite.

But Mr Chalaer's mother and father, who have travelled from China to find their son, believe he has been kidnapped and is still alive.

"From the first day, as parents, our feelings told us our son was not dead," father Hakki Caglar, a Chinese industrial businessman, told Fairfax Media on Thursday.

"Parents sometimes have these feelings. The police said there was no evidence to divert them away from their search but we think he might be taken away. By who, we don't know. "

If someone does have their son, they have appealed to them to give Mr Chalaer insulin as he suffers from Type 1 Diabetes and will die without it.

When Mr Chalaer left his campsite, he didn't have his insulin.

His family believes he wouldn't have been able to wander far without it. The fact police found no trace of him within a six square-kilometre search area indicates to them that something else has happened to their son.

"The only explanation to us is he's not there, he's out of the area," Mr Caglar said.

Hawkesbury crime manager Detective Chief Inspector Paul McHugh said the area he disappeared in is extremely dense, rough terrain and there is no evidence to suggest foul play.

"We're reassessing at the moment as to what we can do with the search and there are investigations going on in the background. We're gathering all the information we possibly can about family, background, work, study, any links with associates, friends," he said.

Mr Chalaer had been in Australia for 18 months studying a masters in hospitality at the Blue Mountains International Hotel Management School.

Classmates, friends and fellow festival-goers have shared his image on social media, desperate to find the man they described as the "epitome of zen".

He attended the bush "doof" festival with three friends on August 6 and didn't know the other 300-or-so guests, his family said.

A photo of him taken the day before he disappeared shows him enjoying himself, smiling and wearing a multi-coloured scarf with his head shaved.

Search efforts were initially hindered because no one realised Mr Chalaer was missing until the Sunday evening, more than 12 hours after he disappeared.

"It's one of those situations where everyone else was assuming he was with someone else, and it was only when people returned to their homes in Sydney they realised he hadn't returned," Chief Inspector Garry Sims said at the time.

Temperatures dipped to 4 degrees during the following nights.

His family are thankful for the huge search effort that involved police, SES, Dog Unit and PolAir but they are heartbroken that resources have been scaled back.

His parents, who raced to Sydney the day their son went missing, have vowed to stay until they find him.

They have spent each day since then going to the area where he went missing, talking to his friends to see if they noticed anything and printing and distributing missing person posters.

At the bottom of the poster, it says: "his family is anxiously waiting for him".

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