oliver pareece jones , 37 , of colorado was last seen at walmart on april 5 .
he was seen in surveillance photo leaving sheraton hotel hours before and withdrew $ 800 in cash from atm and another $ 100 after trip to walmart .
at walmart , he was captured in surveillance footage where investigators said he purchased backpack , radio , and camping gear .
during trip , jones was reportedly mugged and assaulted , and suffered from a concussion ; he was treated at cedars-sinai medical center .
family fears concussion affected his ability to reason or ` do anything '
police were waiting to speak with his cousin on friday who was with him the night before he disappeared .