Easy, now--it's unlikely that the guy is dead. He's just missing! He has mice to eat. He is a snake, he can find his way out if he wants to. If you can't find him, then just wait. Wait, and remember that wild ball pythons can go 6 months or more without food. That they like to sit and wait. That they can take weeks or months to adapt to a change in environment. He may come wandering back out once he feels secure enough to explore, you know. It doesn't sound like he will lack for a source of water, or food. Chances are, he is ok.
Relax--it's true, it may be a long time before you see him again, but that doesn't mean he isn't there. It's clear you have done all you can--now it's time to wait--ball pythons are patient, and that's a lesson they can teach us, too.