If he did that, there was probably something not-quite-right with the mouse. You could have heated it up a little more and offered it again, but since you waited I would just try again next week.

Snakes will recognize food using a variety of senses including temperature, smell, the way the rodent looks, the way it moves, and finally the way it feels in its mouth. Sometimes a snake will refuse to eat if just one of those attributes is off.