Sometimes people are going to find out about social events they are not invited to. It's inevitable. However, etiquette requires that you be circumspect--not secretive. In the case of a new game the kids are playing, there's no need to mention that it was played at a private party previously. You can just say, "Oh, how about let's play this new game" and explain the rules to people who don't know it. In the case of towels or personal items left at another person's house, there's no reason at all to discuss this in front of people that are not involved. I'm saying this not to criticize you for how you handled things, but just to answer your question. (Sorry for the delay. A bunch of LJ replies ended up in my spam box.)