Wow, Blue, so glad you reached out even though you have felt left out. I, too, am very sensitive when it comes to friends, and facebook shares lots of events that I am not invited to. If all of my transgressions were added up for loss of friends tally, I would have no friends at all. My drugging days are long past, but drinking can still get me into trouble. I am overbearing when drinking.
As for all of the partying, it sounds like you and red were willing participants who had lots of fun. It must be a bachelorette parties. I went to one once where the exact same thing happened. One of the girls was openly a lesbian and another wanted to experiment. The rest of us heard loud sex for a while. I think that the non-lesbian had regrets, but she still laughed along with us the next morning.
My final thought, perhaps the fact that you were busy dealing with your children was understood and respected by your friends. Those who commented on facebook sound glad that you have resurfaced! I hope you will be able to go, but I understand the feelings you are having.
Good luck!
Bluemountains