Ok so last night I went to my friends house they all introduced me to this girl that was visiting. Later on in the night we get really drunk and go to this party, at the party she pulls me on to the dance floor and says "lets dance". We end up grinding the whole night and she sits on my lap on the couch. While my friend was at the party the entire time!! He saw me dancing with her, didn't seem to get mad just pulled her away(only after a long time of him seeing us dancing) to talk to her and didn't confront me at all about it. Once I wanted to leave the party he was still super nice to me, asked me if I'm alright and said to stay safe. I didn't realize until this morning that the girl was his girlfriend that was visiting!!!? I feel so terrible, but no one told me I literally did not know at all but I feel so guilty . He didn't introduce her to me as his girlfriend or anything. He didn't say "dude that's my girl " or something so I would at least know. Im not that type of guy that messes with friends girlfriends. How come he didn't confront me or make it known before things got out of hand? It makes absolutely no sense to me. Am I in the wrong here? Any advice?