Sean Sidi was last seen in San Francisco, California on May 21, 2013. He went to visit a former high school teacher in the 100 block of Oak Street at 11:40 a.m. He spoke to his father on his cellular phone at 1:30 p.m. and said he was taking the bus to the park. His phone went dead at 2:00 p.m. His phone last pinged on the eastern end of Golden Gate Park. Before his disappearance, Sean suffered a severe traumatic brain injury in an accidental fall. He's considered medically fragile.