Family members say 19-year-old Sean Sidi went to visit a former high school teacher at 150 Oak St. in San Francisco around 11:40 a.m. on Tuesday May 21. His visit was recorded by surveillance cameras.
He spoke to his father by cellphone around 1:30 p.m., and told him he was catching the bus to "the park." His phone went dead around 2 p.m. and he has not been heard from since.
His family says Sidi is recovering from a brain injury he suffered last year.
The KlaasKids Foundation organized a formal search for Sidi on Sunday. Searchers met at the County Fair Building in Golden Gate Park to plan where they'd look for the teen. New evidence suggests he might have been in the area.
"Initially the police thought that the cellphone ping of Sean's last call was at Baker Beach," said his mother, Lynn Ching. "The reconfigured information is that the cellphone ping came from the east end of Golden Gate Park, which is why we're here today."
The teen's father followed another lead by searching parts of Marin and Sonoma counties Sunday. There has been information that he may have gotten into a car.
Sidi is described as being a slim male of mixed Caucasian and Asian descent, with dark brown hair and eyes and braces on his teeth. He is 5 feet 5 inches tall and weighs 120 pounds.
He was last seen wearing a black and gray North Face hooded rain jacket, blue jeans and black canvas shoes. He recently came out of an arm cast and was wearing a black splint on his left wrist and arm.
Anyone who thinks they may have information on his whereabouts should call San Francisco police Sgt. Ann MacKenzie at (415) 734-3268 or go to www.seansidi.com.
(Bay City News contributed to this report)