Let me start off by saying, I'm sorry you had to experience this scene with your two best friends. I understand your wanting to open up or experiment in your marriage. I have some issues with how it was handled and if you don't mind would like to play devil's advocate from the male point of view.
Your husband's quick, enthusiastic response makes me wonder, if he has in the past, always been faithful, if not physically then atleast emotionally with you. I'm sorry, but he seems wayyyyyy tooooo comfortable or familiar with the emotions of it all. It also makes me wonder how familiar your friend Star has been, too. Obviously, there were communication issues for them to forget you in the bedroom. I still don't see how that could have happened. You took it way better than I would have. It sounds like maybe subliminally they didn't want a threesome, but only to be together themselves. Have they been denying this to themselves for years? The sexual tension may have been overwhelming and all consuming, but I just never, ever in a million years would have forgotten my wife. Something is too weird here for my liking.
There's one thing to be poly and one thing to swing. Which is it you want, which does your husband want? Emotions come with poly.......it's a beast to tame. Swinging is just the opposite, a few sweaty hours, then everyone goes their own way til next meeting. No strings, no feelings, no jealousy, nada.
I hope this reply doesn't upset you but gives you another point of reference from which to address your situation with your two best friends. Good luck.