What would I do if someone used something I created without giving me credit?

Wow what a question to be asked. I have had before work being "stolen" as you would say from me by an old manager where I work. It hurt, because he had no issue about taking the credit right in front of me. I actually gave him a look and cleared my throat at the same time. My old manager in turn, stated "oh yes, sorry it was Shonta who completed and sent out everything to the client." A part of me was glad that he retracted everything, but at the same time I wonder if I did not do what I did if he would have confessed about not being the person who was responsible.