Just the waste product buildup maybe enough to get an animal sick that eats the mouse. Of course, the chance of this maybe small if you only had the mouse thawed out for a short time. I don't want it to hurt my snake. Thawed meat spoils much more quickly than fresh because the cell walls were destroyed by freezing. This allows bacteria to decompose the flesh more easily.
Bacteria build up, as do the waste products of bacteria.
Just the waste product buildup maybe enough to get an animal sick that eats the mouse. Of course, the chance of this maybe small if you only had the mouse thawed out for a short time.