Yeah, they have a habit of doing that. :rolleyes: I had a mouse in a tiny cage that I was saving for Penny after she gobbled down two, and he kept picking up the wood chips and putting them in the water dish. It was quite hilarious, though I would scold it through the plastic that the dish was meant for drinking, not rearranging the wood.
Penny is almost 3 feet, I think, but I still have her on mice. I'm not personally comfortable with feeding her rats just yet. She's still so tiny! And I feed live, so I most certainly refuse to risk it hurting her. Plus, she just plain loves mice. They're never alive in her tank for more than three minutes.
And seeing as that's how mine is, something tells me yours might not actually want something that big. If he still hasn't eaten by today, maybe try a regular sized mouse. Snakes are pretty good judges about what size prey they see and won't normally eat something they think might be too big. (At least that's how it is on the Discovery Channel! :)) Or perhaps it's the color of the rat. Some snakes are picky about their prey color, too.