Like everyone else said - live rodents can and will seriously hurt the snake. However, a trick that has worked at the store I work for is to prekill a mouse/rat, then place it in a paper bag in the snake's cage overnight. This works almost every time for the ground dwelling snakes, and may be worth a shot for you if you haven't tried that already.
Otherwise, keep it separate, leave it alone, and offer food again just once a week! 
My personal opinion is that if you want to leave something in overnight, just prekill a rodent rather than leaving a live one. There is always a chance, however small, that an adult live rodent can seriously injure your snake.
~jenny
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"Polysyllabism in no way insures that what you're saying is actually worth being heard." - Blake (an e-friend of mine)
"I have never made but one prayer to god, a very short one: "O lord, make my enemies ridiculous." And he granted it." - Voltaire