At Will employers may let anyone go at anytime for no reason at all. They don't even have to give a reason. I'm sure they didn't tell you it had anything to do with your medical situation, right? That would be highly illegal.
My husband was let go from a job years ago because he was a 'whistleblower' lol. Whatever the reason was that they gave him, forget what it was, made no sense. We did get an attorney and went back and forth with the company and were able to get a little 'something' out of them.
Turned out to be the best thing that could have ever happened. The previous employer had a pay freeze and kept increasing the out of pocket amount for insurance, etc. Currently, my husband is making almost ten bucks an hour more and all of our health/vision/dental benefits, along with annuity, and retirement fund, are completely paid for by his employer now.
When one door closes, another one opens.