Your nose should tell you if it's a regurgitated rat or poop...while poop never smells "good", a regurge generally makes you want to gag. Is it possible the rat
was bigger than he's used to eating? It's possible he wasn't "warm enough" to digest, but that was probably by his choosing: sometimes you can feed a snake
that is going into shed & their body cannot do both very well (both shedding & digesting require extra hydration from the snake's body) so they regurge the
rat instinctively. Watch & see if he doesn't start clouding up in a few days now. Snakes can sense an impending shed before we can see any obvious signs, so
don't panic & think he is ill...this may be "normal" under the circumstances...rats aren't so easy to digest. What size is your snake & what size rat did you feed?
Another reason snakes go under their water bowl is because it provides "back pressure"...the sense of security they get being in a tight cave, safe from predators.
If their hides are too large, open (large doorways) or lightweight, this may be why he sought to go under the water bowl. If he has larger hides, you can also
stuff some paper in them to make them fit "tighter".
BTW, clean up the mess...
And at least yours is a snake...pretty normal for snakes to like tight places. I actually have a dog that does the same thing...even in hot weather, if he
doesn't have a "blankie" over him, he burrows under his dog bed!? Maybe he was a snake in a "previous incarnation"?LOL