Does an emoloyer have to notify you before termination while you are out under medical leave?

I was out Jan-Mar on FMLA with parents. Worked two days, blacked out on day off and sustained head injury. Went to personnel, worried over job. Was told not to worry, I had up to 6 months. (I had already explained about just returning from FMLA.) i wrongly thought my FMLA and new injury were considered separately. I gave my department regular updates following MD appointments regarding reports, and return to work updates.I received no communication from personnel. While still on medical leave, my position was terminated. I was not notified prior to termination. Had I known this information, I would have done everything in my power to return prior to termination. I now understand I was only allowed six months of medical leave, I just want to know if it was legal not to let me know prior to termination. I received a termination notice about a week after termination date.