How rude can he be?

Grab his arm, snuggle up to him and start nibbling on his ear. Also, whisper sweet nothings in his ear. Tell him how much he means to you. Or - Stick your hand out to your boyfriends' friends and introduce yourself - say in a loud but oh so sugary, sweet voice. 'How nice to meet you. I am Suzie, (or whatever your name is) Roger (or whatever your boyfriend's name is) is just going to go and buy me a pretty necklace (or a bracelet or whatever you want, my dear) isn't that sweet of Roger, he is the sweetest, most generous, most kindness person I have ever known.' Then say, 'Nice to meet you, as you can see, we are on our way.' Then grab your boyfriend's arm and say to him, 'You are so sweet' and start walking away, arm and arm with your boyfriend - towards the jewelry store, of course!

Did you say anything to him about it? I would have. I agree, not only was it rude but it was very disrespectful to you. Is he ashamed that your his girlfriend? That's what I would have thought. I would most definitely say something to him & ask him straight out why he failed to introduce you to all of his friends.