I've had my ball python for 13 years now, and he has escaped a multitude of times. He is a little escape artist (I eventually had to get a cage with a double lock on the lid). Anyways, when ever I would find him it was either near my tv (vcr, xbox, and even under the tv), or the lil guy would be coiled up on my water heater.
If you have looked in all the conventional areas, perhaps try putting a mouse (or guinea pig) in his cage with the lid open. Also, put the cage on the floor. I have tried this only one time, but it worked in a matter of a week. Best of luck to the relocation of your ball python!!!
Also, random inquiry. Was your recent ambilobe purchase from Lance?