Was I wrongfully terminated?

I have worked for a company through a temp agency since March 2015. I have been told on numerous occasions that I would be hired on permanent . On July 14th I suffered a mild heart attack while at work. While waiting for the ambulance, the head of HR told me my job was not in jeopardy. On the 16th I was contacted by the temp agency stating that the company was terminating me due to attendance. I had missed days previously which were approved by my supervisor. I was never wrote up or counseled for any attendance issues. Can they legally do this?