I own three ball pythons, and from personal experience i know firsthand of their ability to escape. They like to find small dark places to crawl up into. They are very timid animals, and therefore need to feel secure in their environment. Check all small dark areas. Ive found my pythons in speaker boxes, and in the upper inner edges of my desk. They arent known for being arboreal, but they are superb climbers! Good look in your hunt. Im sure he'll turn up.