I can safely tell you that the casinos think ahead on exactly these issues, and you got pretty lucky. In any case I can say that if your chip amount was not (evidently) small, and the teller hadn't known you, you would not have gotten your chips cashed in, because the first line of defense by the casinos in this case is to say that they do not cash outsider chips, in case they are stolen!
Anyway I have read an online source addressing your question, reminding you that chips are not cash.. You can see it at this casino
I can also safely say that this tourney did not take place in vegas… sounds more like a charity tourney…