If you leave it in over night, definitely throw it out in the morning. The only time I ever re-freeze is when I know right away my snakes aren't at all interested in eating, then I'll throw it back in the freezer, but I never re-freeze more than once. I usually only re-freeze large rats too because they are much more expensive than fuzzies. If you can afford to throw them out, that's probably a better option. How much does your bp weigh? What's your setup like? How many days have you given him to settle in? There may be something else going on if he isn't eating.