I am from Ohio and recently was on medical leave. I wasn't released from medical leave until 2 wks after my FMLA was up. My supervisor advised me that he had no intention of replacing me as long as i returned in Jan. (which I would have), and my job would still be there when I returned. When I was released from medical leave I was advised my position was no longer available because of restructuring. I have just learned that the restructuring may not of actually happened and I was lied to. Would I be able to claim promissory estopple and sue?

Probably not, unless you have the promise in writing.

Promissory estoppel is tough to prove and really the best evidence is a writing documenting the agreement. Did anybody witness his statement to you?