gen xer, you are a much better (wo)man than I. There is no way a guy I didn't care for, who wasn't invited, who puked all over a friend's house would ever cross my threshold.
I'd also be giving Ron and Amy an ultimatum. 'Bob is not invited. Do not bring him with you. If you do bring him with you, I will not allow him in my home. If you are his ride, you will have to figure out how to get him home. And if you do bring him, unfortunately, I won't be able to invite you to any more events I host for fear that you will bring him again.'