what happened after the party (my first blog)

so after the party it was the spring holidays yk so we got invited by friends to their house and everything but the last Sunday at 11 pm my bsf that wasn't at our party (the gf of the guy being massaged by his ex) texted me and my brother on a gc that we had to hangout cuz she lives in the same village as us and she said : guys if you didn't know me and my bf broke up bcuz he cheated on me with one of my bsf at your party. and I was shocked cuz I knew they slept together and when I woke up I had a feeling that something happened right so yeah I was right this whole time and mind you I had to apologize bcuz I was ruining their relationship. What would you do at my place? Was I right ?