(Portland, OR)  --  Authorities are searching for a Portland man who vanished Saturday.  Officials say 68-year-old Thomas Branch McAdams's car was found yesterday at Horsetail Falls in the Columbia Gorge.  It's not known whether McAdams, who recently showed signs of memory loss, went on a hike, as he left his regular hiking gear at home.  McAdams is described as white, five-feet-eleven, 165 pounds, with gray hair and green eyes.  Anyone with information is asked to call 503-823-3333.