Why is behaving this way?

I went to a friends party and I kissed one of our mutual friends. When the guy who invited me (keep in mind he has a gf) came in the room, the kids told him what happened and he said in disbelief "No they didn't " and the other people were telling him that it was true. Later, he got one of his other friends to ask me about how the kiss happened and the guy ended up telling him that I liked the guy I kissed and that he I wasn't sure what the kiss meant.(Which is what I told his friend). Why couldn't he have asked his friend that I kissed? They are besties after all. This guy that invited me also friend zoned me months ago. What was his deal here?