Robert,

Yes, my snakes used to get up there, and seem to get stuck, too! They're in a 40 gal, now, and have learned they won't get hurt if they drop back down. The babies can't get up there, yet, but I'm sure it's just a matter of time.

Also, you can build a hide for them that looks great, and is super cheap to do. Here are some pics of mine:

















Unfortunately the pics are in reverse order, but you get the idea of the evolution of the project. You can also use Great Stuff foam insulation to build hides for them. While you'll put in a good deal of work, it's fun, and cheap, so treat the hides as disposable objects, not art gallery pieces to be treasured forever. If they get yucky, make new ones, this first one I built doesn't seem to be as waterproof as I'd like so I don't put it in the dishwasher, nor do I soak it when cleaning, just spot clean with a vinegar water solution as necessary.

Supplies:
Old foam
Old cardboard boxes
PVC scraps
Hot Glue
Laticrete
Grey Silicone Caulk
Stone look spray paint.

If you rip the foam apart, rather than cutting it, you'll get a rough edge more like stone.
Hot glue your foam pieces, box parts, pvc etc. together into your final shape.
Coat with Laticrete, may take several coats, with 24 hours dry time in between (clean up your work station so your parents are freaking about the "extra mess that darn snake creates" in between phases)
Once it's thoroughly coated, wearing gloves and using a foam brush, pat on the silicone. May take a few touch ups. Let dry completely.
Spray with faux stone paint.
Seal if desired with a matte spray.
Set in cage and watch your snakes play!

You can also make little holes in the "rock" and, when the project is complete, stick some fake plants in them. Make it look as natural as possible, choose wispy grass, or flowing creepers.

have fun!