Somehow I've had this happen to me a lot. The exact same comment, every single time. "Did you forget your name?" "Oh you forgot your name!" "Haha forgot your own name?" and certain other variations of it. Eventually I've managed to say my name in due time. Most of the times I just smile and move on. Though I do recall on certain occasions being fed up with these remarks and saying something similar to what you did. Most people shut up and apologise. I don't know why people do it. Why pass a snarky snide remark to someone you can see is visibly struggling with something? Anyway, I'm glad you stood up for yourself.