If you're worried and since he's young, I read you might try the soaking as suggested above but add some pedialyte to the water so he can get a few nutrients as well. I don't know how young he is but I wouldn't imagine a hatchling could go a long time without eating. If he's big enough to eat adult mice I would imagine he's fine, just dehydrated. Try a live hopper if he won't eat his regular f/t meal as long as he isn't weak.