TW for outing...........................I accidentally outed someone and I feel awful

Hi there,
So my friend was talking about a person he'd seen me with and misgendered that person. This person is non-binary and uses gender neutral pronouns and I automatically corrected my friend without thinking. He doesn't actually know this person in real life, and has never spoken to them before.
I'm pretty sure this person is open about their gender and things like their facebook gender have been changed to "non-binary" but I still feel absolutely terrible for doing this. What should I do? Is it okay because my friend doesn't actually know them?
Thanks for the help; I feel terrible about this.