How Can I dispute a false accusation and get it removed from my record?

I was accused of saying that I wanted the world to end and that I wanted to hit people over the head by a coworker where I currently am a Temp worker. The first, while close to what I said, was not quite correct and taken out of context. My coworkers and I were discussing the Mayan calendar and the supposed end of the world. I said that I really didn't mind if it did because then I wouldn't have to pay bills anymore. This was said in jest but apparently taken wrong by someone who was listening to our conversation. The second accused comment I neither said or ever admitted to saying. My current manager didn't believe me and has had me on a medical leave. They decided that since I didn't care if the end of the world came, I must want to die so therefore I must be suicidal. While I do have a mental illness and suffer from depression and anxiety for which they are aware, it does not effect my work. My managers attitude is that I need to prove it. How does one prove something they Didn't say? Also I fulfilled all the requirements of speaking with a help line and getting a doctor's note allowing my return to work 2 weeks ago and she was supposed to call me to tell me when I can come back to work. She was supposed to call yesterday so I could come to work starting today but after not hearing from her and leaving a message yesterday and today, I still have no information on when I will return to work. I am home without pay but techinically still employed. I need this removed from my record as it isn't true and will keep me from getting a position in other parts of the company. I need them to decide whether they are letting me go so I can apply for unemployment or reinstate me and let me get back to work without the bad reputation. What are my legal options? What can I do or should I just cut my losses and leave?