One of my ball pythons, Whiskey, got out the other night while I was at work. I absentmindedly forgot to secure the lid to his tank and the little 165 gram Houdini took full advantage of that. My wife texted me about half way through my shift and said that one of my snakes was out, and in our master bath. He had slipped into a little 2 inch wide gap under the bathroom cabinet. Every time my wife approached him, he'd pull back into his hiding spot. I asked her to rolled up some towels and placed them under our closet door and bedroom door and I would search for him when I got home later that night. My thinking was that when the room was dark, he'd come out to explore - I, luckily was correct. When I got home he was "strolling" along the tiles near the toilet. I easily picked him up, gave him a quick once over, placed him back in his tank, and made sure to secure the lid and went to bed. I did a through exam later in the morning and he was fine.
My advice would be to make the room(s) as dark as possible, and maybe the little bugger will come out. Good luck.