Update on my last post: he was cheating

The original is here if anyone wants it. https://www.reddit.com/r/FemaleDatingStrategy/comments/frhs2n/broke_up_need_some_validation_that_hes_a_lvm/

Yeah. He had his relationship status hidden on facebook, but I've just accidentally found the woman while I was browsing and she's listed as "in a relationship" with him.

I went back to the website where I initially met him and said: "[Name]?"

He said: "Yes?"

I said: "I've found [her name] on Facebook, delete yourself off here, fuckboi."

And he said, "Okay." And he's either deleted himself or blocked me.

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Did I learn anything? I think I shouldn't have quieted my gut instinct, like telling myself "Oh you're so suspicious, you don't see the good in him" etc. At least I got out of there after three weeks instead of a year like I would have done when I was younger.

Edited to add: r/SpectralCadence has pointed out that letting men know what they've done makes them smarter about hiding from the SO. I'm open to advice about whether I should contact the woman he's in a relationship with, or what to do. Thanks.