It's perfectly normal. Ball Pythons are very secretive snakes. A hiding Ball Python is a happy Ball Python. Awesome pets, but not great display snakes.

I was wondering if your snake have ever hid so well you thought it got out
Once I had my first BP in a plastic display enclosure with sliding glass on the front. One night he crawled up on the thin ledge above the glass sliding door and I looked in and thought he had escaped and looked all around the snake room for a good hour before glancing over at the tank and seeing his head peaking down from the ledge and looking at me. Had a look on his face like "HA I got you!" Could NOT believe it.