You know what they say about assumptions don't you?

I agree this person should be locked in a room without water for 48 hours! (if you saw it didn't have water two days earlier why didn't you say something then?)
This employee promptly fixed the situation as soon as it was addressed. I'm pretty sure that there was more people in that store then just you. And I'm also sure that someone else would have said something aswell if it was seen.
I'm just saying that this is hardly a bad thing that happened at this chain store. Now a cricket eating ball python is bad.
But on the short, this person is horrible! They probably purposely flipped over the dish in an irate temper tantrum and removed it's hide to watch it suffer! (insert evil laugh)
You see the two sides of the coin now?
Option 1 - snake goes 48 hours with no water and hide due to employee enjoying the animals suffering
option 2 - return from earlier that day/ multi tasking and cleaning cages (happens all the time) and was distracted not getting a chance to flip the dish and set up the cage (yet).

(thought I'd give some more of that "reeeal cool" sarcasm.)