Like the others mentioned, it isn't a big deal.

It might help for you to warm the head end of the mouse slightly more than the bottom end.

I typically let the mouse thaw to room temperature then place them in a sealed plastic bag and soak them in the hottest water my tap can produce head first. This way the tail end typically is not fully submerged and the top half becomes the warmest region on the mouse.

Don't know if this will help but I guess it's worth a shot