(Vancouver, WA)  --  Police in Vancouver, Washington are searching for a man who went missing during a bike ride with his adult son.  Police say 66-year-old Robert Robinson became separated from his son Saturday night while the two were riding their bicycles on the I-5 freeway bridge to Vancouver.  Family members say Robinson suffers from a medical condition that causes problems with his thinking abilities and memory.  Anyone with information on his whereabouts is urged to contact police.