Please read our thread on "You know you have lupus fog if" and you will find lots and lots of stories about how we forget things, do crazy things, miss important things, etc.
Your friend should be chastised for her reaction. Whatever happened to being an understanding and supportive friend??? I'm not sure if your boyfriend's explanation was meant to be helpful or a criticism.
Regardless, I agree that their reactions were uncalled for and most importantly, YOU MUST NOT THINK LESS OF YOURSELF FOR HAVING DONE THIS SIMPLE THING!!! So many of us have done so much worse and we all MUST find a way to laugh at ourselves. These things do not diminish us as human beings, nor do they have any bearing on our intelligence! Remember that!
I wish you the very best.
Peace and Blessings
Look For The Good and Praise It!