I'm sorry to hear that this happened to you. I was thinking that maybe they are using that one mistake as an excuse as to why they fired you. But did you ever sign one of those "at will" papers? If you did, which a lot of places make you do anymore, then sadly they could fire you without any notice or anything. I know it sucks though. That's really sad if they are firing you over one mistake, especially since you had only been there for 2 weeks. But it's their loss!!!