Once I was notified from my management that I had been part of some injustice against some woman and therefore I am no longer welcome to do business with them. My manager asked me what it was but I could only guess. I tried to ask colleagues if there was some rumour about such an event of if somebody could confirm what it was. We still don't know more about it. I have tried to have the claim investigated and the people I speak with can also only speculate what it was. I was told by the authorities and also colleagues that it is an "anti-pattern" and if I actually was unfair somewhere then the right thing to do would be to inform me so that I could apologize or regret what I did. But now I am cynic and angry that nobody even confirmed or told me who, what, where, when. Only why: That I had been unfair completely unspecified.
I can see two main things that I don't think would be received well:
You say your management notified you that you "had been part of some injustice against some woman", and then that they asked you what it was. That's really confusing. I think you mean that you were fired but not really told why, but I'm not confident about that. It will be helpful to your question if you make that part clearer.
The initial version of your text doesn't contain an actual question, just a description of the situation you're in. You say in the comments that your goal is to find out "How to deal with a "workplace-related" event when nobody knows what it is". That should be in your question post, otherwise it will attract close votes (as gnat alluded to in the comments).
I'd also suggest you add paragraphs and trim the "story" part a bit, to leave only the most high level points. It may still get closed as off-topic or a duplicate, but I think there's a good question in there.
Maybe something like:
I was called into a meeting by my management, told that I had been part of an injustice against a woman, and fired. [I'm guessing that's what you meant - change as appropriate]. During the meeting my manager would not tell me what it was, and said that I should know already. [This is absolute speculation on my part, but it seems like it might be what happened? Change it to the real story, but keep it short]
I have been unable to find out what they were referring to, and my efforts have only been met with speculation. I've also been told that if I actually was unfair somewhere then the right thing to do would be to inform me so that I could apologize and make amends for what I did. [I believe my change to your wording here is important. If you write as if you want to dismiss any real wrongdoing (if it turns out it existed) then people are likely to focus on that.]
I am cynical and angry that nobody even confirmed or told me who, what, where, when. How can I move on from an event like this? [ <-This last sentence is where you need to specify your goal. The one I've written isn't very good, and would likely get closed as "too broad". You need to specify what you want to achieve, as specifically as you can]