Ah, that's messed. Sorry you had to deal with drama-assed shit like that, Christine.
I had a fuck buddy once, who swore to me he didn't have a girlfriend, and one night that we slept together he told me he had to leave early for work, so we both had to leave soon, which I did.
Ended up he was leaving on a weekend vacation with his girlfriend.
Soon after, she confronted me, suspecting her boyfriend was cheating on her, and asked me if he had told me about her, which he did, but in the "she's only a friend" capacity. Oh Holy Night was I wrong.
That's when she told me the bondage equipment we used that night was hers ;)