
I was in a situation like that, it's not a good feeling. My friend's ex-fiancee thought she was having an affair with me because we were always hanging out. He lived in NY and we lived in Cali so she would get lonely and we'd have sleepovers all the time. One of his friends told him and their mutual friends that we were having an affair and her fiancee believed him. He didnt listen to her and called us sluts (we're both girls) and other unflattering names and broke up with her. Then there months later he showed up at my dorm since she was over and he tried apologizing and tried to get back with her. She didnt, since it wasn't the first time he acted that way. I still feel guilty even though it's been 6 yrs. We didn't do anything bad and were like sisters but maybe the way we acted seemed wrong to people and I ruined their relationship. It's all pretty crazy

I've have had two of those "affairs" myself: The first one was with a college buddy across the street. He called me outside to tell me about it, and we were both like "it must not have been very good, cause we don't remember a thing!" When I mentioned it to my mother, she started laughing. Apparently, she could pick up wireless phones in the area on her CB radio, and his wife was the one spreading the rumor!
"Affair" #2: some guy called my house phone, and told me my # was on his bill, and I'm like "that's not possible, I'll call the phone co" (click). His wife . . . . visited my mothers house . . . . claiming we were having an affair (I don't know these people!). They must have picked up an old phone book of when I used to live there, because that was the wrong house! I took my brothers baseball bat home with me that night.

That is horrible and so sad. Honestly its not your fault the fact that he thought you two were having an affair just because you were close means that sooner or later he would blow up like that anyway. I would say its a good thing you guys found this out before it was too late otherwise she would be married to a toxic man.
I feel so bad for Noah imagine how gross it would be if you and a close friend were rumoured to be having an affair oh god i'd die