Can employers "restructure" a part time employee that was on medical leave out of their job with no reason given?

I had been an employee of Forward Air Inc. for around 7 years. I was a full time employee from 2007 until Fall of 2010 when I dropped down to part time employee status so that I could return to college. Over all of the years of my employment I had never had any complaints about my work and had always received positive reviews. In May of 2014, I required some medical treatments which made me unable to work. I was not even able to drive while receiving these treatments. I began receiving Electroconvulsive therapy on May 7, 2014 and received these treatments until August 8, 2014. During this time, sometime in June or July, I received a call at home one Sunday from the Station Manager and he proceeded to tell me that they were doing some "restructuring" and that I was losing my job. I said, "so, I'm being fired while I'm on medical leave" and he would never use the term "fired" or give me any reason as to why I was being let go. I'm also wondering if I am eligible for unemployment benefits