I'm not trying to be rude, but this is a case of whether you want to risk getting your snake sick, or spend a few extra bucks to get a fresh rat. If it were to make your snake sick you may be paying hundreds of dollars in vet bills so if I had any doubt, I'd just get a fresh one. Wouldn't want to risk it. That is just part of snake ownership. Sometimes, they just don't eat, and you just have to deal with it.