The Vancouver Police Department says that what is known is that the 16-year-old left a house party the night before, and was last seen at around 11 p.m. PT in the south lane of E. 60th Avenue near Inverness Street.
Seven hours later, at around 6 a.m. PT, the teen was shirtless, shoeless and bleeding when he knocked on the door of a house on E. 60th Avenue near Ross Street, asking for help.
"He was taken to hospital where he was diagnosed as having suffered a possible stab wound to the chest, a collapsed lung and scrapes and bruises to his face," the department said in a written statement.
Sgt. Randy Fincham said the teenager's cellphone, wallet and jewelry was missing.
Fincham said someone knows what happened to the teen between 11 p.m. on Halloween and 6 a.m. on Nov. 1, and police are asking anyone with information to come forward.
"There are pieces to this puzzle that are still missing," Fincham said.
The 16-year-old is South Asian and has short black hair and a moustache. He was wearing a black toque and a silver chain around his neck that night.
The Vancouver Police Department's major crime section can be reached at 604-717-2541, and CrimeStoppers can be reached at 1-800-222-8477.