FMLA Entitlement Denied by Manager

I've worked 9 years for a company that's aware of my family health conditions. My wife and I have used FMLA. In an unforeseeable situation in which my health was aggrivated (I have a bladder contition), I asked to use FMLA. My manager said: "my FMLA was expired and I was not protected; if I did not show up for work I would not have a job; I was not allowed to step foot on the property or the police would be called." During the telephone request (in tears, pain & despair) the manager accepted my "resignation" and I was terminated. In fact, my FMLA certification states my duration of condition is through April 2009. I emailed HR and said "I believe my entitlement to FMLA was violated." The HR Director responded saying "I will look into the matter." Please, any help, advice or suggestions on how best to proceed? I am also afraid of a hostile environment if brought back to work.