An autistic teen lost for two days in Australian bushland was reunited with his family Wednesday, after a hundreds-strong volunteer search than involved using Vegemite and the Thomas the Tank Engine theme tune as lures.

Will Callaghan, a teen with non-verbal autism, became separated from his family on the summit of Mount Disappointment near Melbourne on Monday, but was found by a volunteer after two nights exposed to freezing temperatures.

William's mother said she hoped the smell of barbecue would coax her missing autistic son into approaching someone for help
William's mother said she hoped the smell of barbecue would coax her missing autistic son into approaching someone for help AFP / SEBASTIAN WILLNOW

"I am really overwhelmed, he's as well as can be expected" said visibly relieved mother Penny Callaghan after the 14-year-old was discovered. "Thank you everyone! I'm so grateful!"

Residents living nearby joined the manhunt and had been asked to barbeque bacon and onions and to leave out his favourite foods in hope his favourite smells would draw the boy out of the bush.

Police inspector Christine Lalor had called for Vegemite and feta to be left out as officers set up three loudspeakers in the area to play songs from Thomas the Tank Engine.

Will Callaghan became separated from his family on the summit of Mount Disappointment near Melbourne on Monday, but was found by a volunteer after two nights exposed to freezing temperatures
Will Callaghan became separated from his family on the summit of Mount Disappointment near Melbourne on Monday, but was found by a volunteer after two nights exposed to freezing temperatures VICTORIA POLICE / Handout

Volunteer Ben Gibbs told public broadcaster ABC that he had been breaking through thick bushland when the boy appeared just metres (yards) away.

"He was really angelic, just standing there" said Gibbs. "I heard he liked Thomas the Tank so I just talked to him about Diesel (a character) and stuff like that."

Will Callaghan's discovery had garnered wide public attention and was met with relief.

Temperatures had dropped below zero degrees Celsius (32 degrees Fahrenheit) in the area Monday night, sparking fears for his safety in what police described as "life-threatening" conditions.

Victoria state premier Dan Andrews welcomed the news: "It might be named Mount Disappointment, but there's absolutely nothing disappointing about today."