Friend told the counselor something

ok this could be a tough one to understand but… my friend (who is a guy)(AND WE ARE IN COLLEGE) but we are both freshmen so maybe you would understand if you were! so we were talking and playing around in the parking lot joking laughing you know having fun! and then he said he had to change in the PE bathroom because it was right there and its a pretty big bathroom!! but there are guys and girls bathrooms you know. so any way I wanted to tell him something really funny and I yelled in there and it echoed a lot and mid sentence he walked across the room to where I could see him as he was walking he gave me a cute little smile and a little laugh as if to say the first part of the joke was funny and I kinda smiled too when he walked by in his underwear but thats not the point of the story the next school day we had together he went to the counselor’s office and wanted to talk with me with the counselor about this but he was already talking to the counselor about this before I knew he was talking to the counselor. so I looked behind me and there he was and I was going to go up to him and say hi! but another counselor had a strange face and said come into this office. now I had no idea what was going on but I found out my friend told the counselor that I went into the guys bathroom and he did not like it and he felt uncomfortable that I just stuck my head in there and told him a joke he seemed comfortable when I went in there but I guess my question is WHY DID HE TELL THE COUNSELOR THAT? AND EVERY THING GIVE ME FEED BACK AND TELL ME IF YOU EVER HAD THIS PROBLEM!!