Police and at least 10 volunteer searchers spent most of Monday looking around Fisher’s Landing and Cascade Park for a missing man.Robert Grainger apparently left his pants and other clothing on a hook and left wearing only a dark T-shirt and his white boxer undershorts at about 4 a.m. Police believe he may be suffering from an as-yet-unidentified medical problem, or possibly the effects of recent shoulder surgery.Grainger’s home is in the 16600 block of Southeast 34th Way in Fisher’s Landing.Two search dogs, one a bloodhound, tried to sniff out Grainger’s trail. Officers with the Vancouver Police Department and Clark County Sheriff’s Office were helping about 10 trained volunteer searchers. But as of late Monday night they had found no trace of Grainger — and no explanation for why he left home.“We’ve got no leads and it’s about the strangest missing-person case I’ve dealt with in quite a while,” Vancouver police Cmdr. George Delgado said shortly after nightfall. He’s “just a normal everyday good citizen. There’s nothing suspicious whatsoever, except the man is gone. There’s just no rhyme or reason to this.” Grainger’s wife and other family members are cooperating with police in the search, including inside the family’s home, for any explanation. No notes to explain why he left were found and all his clothing is believed to be accounted for.Grainger is not believed to have argued with any family members, or to have any other emotional reasons for being upset and leaving his home.