Happens to me a lot. With dreams and stories. If I've told someone something weird, in say, a joke or something, I can often end up thinking that was what had actually happened.
It's a very strange sensation. The same thing can happen with dreams, I don't often think that is what happened, but sometimes I can be confused as if it really happened. So I can sit for ages, going over memories, trying to figure out if they actually happened.
I've tried occasionally asking people who were there, but a lot of the time they laugh it off or something.
Then on top of that, I can't trust my own thoughts. It's a fun life.