I mean you said it to the GM yourself. “You have a hunch what this is about” implying you made some dark jokes. That’s what your supposed to do, look back over yourself and check yourself,

you’re not a child, you’re responsible for your actions and remembering said actions. And maybe try to look at your actions through the lens of someone else who may have found it offensive.

And keep in mind, they can’t just tell you exactly what you said cause that would give you a clue to who reported you like when and where and to whom you said things, now a GM giving out information that would allow a reported player to go back and attack who reported you is bad and they simply can’t do that. And if that isn’t clear to you why they can’t, then I really don’t know what to say.