I feel your pain. I like to let out a deep sigh when something like that happens and I just try to forget about it. Think about it. How many memories of stuttering can you think of in the past couple of years? Send your friends a text telling them how you felt and keep it short. Something like,"Hey, you were kinda lame last night when I stuttered." Don't even respond back if they apologize. If they meant it, they will apologize to you in person the next time they see you as well.