Can i be fired because i ran out of FMLA time when the reason I was out was because I was injured at work?

I filed a work mans comp claim but it was denied because they argued I had a previous condition which isn't true. I am in appeals now. I don't understand how I could legally get fired when i was injured because someone left a cart in the middle of the isle and I fell over it. I had foot surgery last October and I only had 2 weeks left of FMLA. I am also upset because when they were firing me on the phone they had someone in the office as a witness. I told them that they have given me no choice but to file a work mans comp claim. I was trying to avoid that because I didn't want to rock the boat so to speak because they were already laying people off. I did have an accident report on file. My HR director didn't excuse the witness from her office and proceeded to read off personal medical information from a report my doctor had sent her. Isn't that a HIPPA violation? I don't know what my next step should be or am I just screwed out of my job and my privacy because I fell and was injured at work?