Did you file for unemployment insurance? If they fired you for one event, without warnings or prior problems, particularly since you claim it was health related, you'd probably qualify for that (providing you were monetarily eligible. But unemployment insurance, ADA, and FMLA are three unrelated programs. You do not really have to have a major serious awful illness or medical issue to qualify for FMLA, just that you had FMLA does not indicate it was a severe condition. just that it was something that your doctor says you need to be away from work for, and you've been on the job long enough, and they have enough employees.
For ADA accommodation, you would need to have requested an accommodation for a medical reason with documentation. It sounds as though this was not a regular on going issue that you'd been having a lot of problems with, so that you would've needed to have accommodation made for you. It was sort of a "flare up," as you put it.
If they hadn't terminated you, you might have been wise to go through the process of requesting an accommodation but now it's a little too late. They are an "at will" employer in an "at will" state, and they have the legal right to fire you for anything at any time. Unemployment insurance is your only recourse from the sound of this.
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Okay, having read your other post, I gather that you were sort of foolish that you didn't tell the employer the nature of your illness, that you did have a major health situation when you were on FMLA before, and that you didn't ask for ADA accommodations.
REGARDLESS of what else you do regarding your termination, file for unemployment benefits immediately. Your employer is trying to get rid of you. The HR person who told you "there are some things that only take one occurance" to be a reason to fire you is full of it! She's going for claiming, to keep you from drawing unemployment benefits, that this was "gross misconduct," in other words, something so bad that you should not have done it and knew it was wrong to do it even once.
Going in the bathroom and deliberately stopping up all the commodes might have been that. Having such bowel problems that you had to be late coming back from break is not. And the employer does not get to decide whether it is or not, that is the responsibility of the unemployment system. They'll gather all the facts.
If it later turns out that you might have a case where FMLA was violated, you were terminated in violation of any federal labor law, whatever, you STILL need to file for unemployment benefits now. You'll need something to live on until you find another job and you'll be a long time processing any other labor issues that might be involved here. Unemployment, ADA, FMLA, EEOC, all these things do not intermingle, do not share information with each other and are separate entitites.
When you are fired for any reason, first you file for unemployment, then you work on the other issues.
Answer cbg's questions please.