I have been on disability since 2-9-09 for a hysterectomy.?

I called my boss friday because he wanted me to go for a meeting before I returned for work. I wanted to let him know if we could do the meeting on mon. morning like always and he told me that is what he wanted to discuss is that there would not be anymore monday mornings for me, that my position is done. Can he fire me while on disiability. Please let me know.