We're by no means questioning your husbandry. I'm sure its better then mine.

The thing is, ball pythons do escape just because. When I had 12, 3 of them escaped in 1 night and I found them in rather cold places. Why leave when they have all they need in their tubs? Just because.

I'm sure you know that if a snake can get its head through something, almost guaranteed that the rest of the body will follow. I would suggest that you close everything up and do a twice over looking for ANY opening. If you find one, tug on it a little to see if there is any flex, if there is, fix it. Locks on the front don't help anything if there is other places she can wiggle into.