Congratulations! I've had the incredible pleasure and priviledge of watching my wife with other man in a few occasions as well. Many men fantasize about it, but few get the experience the incredible thrill it really is.
How did it all happen for your wife at the party? Did she find a room to play with him, stay out in the open for all to watch? What did they do together? How was the ride home with her and afterwards? Does she have any regrets, or desires to do it again?
Several years ago, I also had the pleasure of watching my wife get fucked at a pool party. The difference is, she doesn't know that I saw her, and I know the guy that fucked her. It was my brother. She was very drunk and he fucked her behind the garage up against the fence. To my knowledge that was the only time.