Maybe I'm reading between the lines here, but it sounds to me as if the OP is only feeding one snake, while I'm pretty sure that you don't thaw just one rodent at a time?
Would that be an accurate assumption? I have heard of some breeders or keepers of larger snake collections say they thaw a BUNCH of frozen rodents all day, or over-
night, but in that case, they stay cold (relatively unspoiled) for FAR longer than just one. I don't have to wonder IF the OP's rodent was spoiled, it obviously was.And even if you can "get away with it", feeding spoiled prey to our pets is not what I'd call "best practices" nor anything I'd feel good about doing.