to back up what LGray23 said,,,, its best to leave it in there (if its dead) even overnight,,, without disturbing the snake.... after i feed my small ones,, or the ocasional picky eater,,, ill either cover up thier tub so as its dark,, ir if its dark outside,, ill turn the lights out in the snake room. ( i use natural light cycles)
BTW,,, if its still in there in the morning,, put it (the rat) in a sandwich bag, run it under HOT, HOT water and get it good and hot, and try to offer again!
spooky