10/02/2011 11:45 EDT | Updated 12/02/2011 05:12 EST

Parents worry about 15-year-old son's disappearance from Toronto hospital

TORONTO - The parents of a 15-year-old boy who went missing from a Toronto hospital said on Sunday say they were extremely worried about his health and safety.

Police have asked the public to help find Robert Frydman, who was last seen at Sick Children's Hospital wearing grey sweat pants and sweatshirt.

His mother, Daniele Gauvin, said Robert was disoriented and weak when he left the hospital at some point early Saturday morning.

With each passing hour, Gauvin became increasingly concerned about her son, who had been missing in cold, wet weather.

"We are very worried that he may have spent the last two cold rainy nights curled up in an alley for warmth somewhere, or that he’s somewhere warm but not safe for him," Gauvin said.

"It’s crucial that we keep looking for him."

Gauvin left her son's side Friday night and was told to return to the hospital at 9:30 a.m. Saturday to have breakfast with him.

He vanished before she returned.

Frydman, a Grade 10 student at a Toronto high school, was an active student and athlete. But his parents said that in the last few months his behaviour changed and his grades dropped.

He appeared unable to sleep and was "simply not himself anymore at the start of the school year," Gauvin said.

Frydman checked into Sick Children's hospital on Sept. 25 for evaluation. He was transferred to another facility two days later but sent back to Sick Kids Thursday for dehydration.

Gauvin said the usually active teen was sick and confused, but made it clear he did not want to be in hospital.

"He was in secure conditions when I left, and what happened next is not known, nor is it something we are focusing on when his safety is at stake," she added.

"We urge everyone to keep up their efforts for his safe return."

Frydman is about five feet six inches and 125 pounds, with a slim build, short brown hair and dark eyes.

Anyone who may have seen him is asked to contact the Toronto police, 52 division.