I've been asked multiple times over the years.. "did you forget your name "? They didnt know I had a stutter and only found out when I blocked on my name. It wasnt malicious and they've all apologized.. As long as it's not an issue moving forward them a simple "hey,sorry about that.. I didnt know." Should be enough. If the person holds a grudge then theres not much you can do at that point really 🙃🙂