I'm sure someone else will chime in with more experience. If that happens again I guess you can try hitting the mouse/rat in the head with the tongs to try and knock it out. However, I don't think that is a good idea. You could cause the snake to refuse the mouse and not feed that day. Then you have a half dead mouse or dead mouse that you have to deal with. Personally, once the snake has struck and started to constrict, I don't put my hands or anything else back in the tank at all.
Best thing to do so you don't have to deal with that again is to get it on f/t, and hopefully you can get your ball to take f/t from there on.