OK, how big an old is your noodle? When did it eat last? Have you ever had field mice in your house?
If you want to find him after having the run of the place your gonna have to stay up or wake up at 2a.m.
Have all the lights off an tv or anything that makes noise. Just sit an wait. You'll hear him moving "if" he isn't under the house or in the walls.
If you've had mice, then he's following old smell an in the wall.
A live mouse or small rat in a cage in the middle of a room can draw him out.
An check your linen closet. You won't be the first one to grab a towel an have a friend with you.
Good luck!