Matthew Allen’s family feared the worst after the 18-year-old disappeared in late November from Westleigh, near Cherrybrook in northwest Sydney and his mobile phone and bank accounts went untouched.
Extensive searches of the area by police failed to find a trace of Allen, who suffers from an undisclosed medical condition.
But two hikers spotted the teen lying in bushland less than two kilometers (just over a mile) from his home on Saturday, covered in leeches and insect bites and having lost almost half his body weight.
He was partially blind, exhausted and suffering gangrene to his lower legs and feet after an ordeal police said they were amazed he had survived.
“He was completely exhausted, completely dehydrated, suffered significant weight loss, somewhere up to 50 percent. He was suffering from partial blindness and he had leeches all over him,” said acting police inspector Glyn Baker.
“He was not living under any shelter and was exposed to the full conditions since reported being missing,” he added.
Allen was believed to have deliberately hidden himself from view in the area which is heavily frequented by hikers.
He told rescuers he had survived by drinking from a local creek, which was almost dry when he was found. Allen endured soaring temperatures in recent weeks including a record-breaking 46 degree Celsius (115 Fahrenheit) day in Sydney.
Allen was airlifted to safety and was undergoing treatment in hospital for his injuries, which were described as not life-threatening.
Police have yet to speak to him about his ordeal.
“His family are ecstatic that he’s alive and that he’s well,” said Baker.