I was fired from GM 3 days before I was to be hired in.?

I was fired because my supervisor said I falsified part numbers on 3 different occasions. When we had the meeting the 37 numbers he thought he had dwindled down to 5 part numbers I could not account for. Now I just found out that a guy I worked with that was not near his hire in date was suspended for doing the same thing. except he was not fired. Is there anything I can do, the union pretty much sucks ?