Should I have told his girlfriend that he cheated?

splashofyellow
So, I met this guy in a bar and we ended up hooking up. I lost one of my earrings there so I looked him up on facebook to ask if he had found it. It didn't require much detective work as he told me his last name.

While I was looking at his profile, I noticed that he had a girlfriend. I felt like an idiot. Not for a second did that thought ever cross my mind. I left him a passive-aggressive message that was kinda pointless and stupid but I felt like I had to let him know that I was mad about it and that it wasn't an okay thing to do. After seeing the message, he obviously blocked me on facebook. Which is fine cause I don't have any plans of seeing him again.

But I started thinking, should I have told his girlfriend? I don't want to intentionally hurt her because it's not her fault that her boyfriend is a jerk. But on the other hand, I think she deserves to know. At that time, I decided that it wasn't my place to meddle. But was I wrong not to tell her? For all I know, he could have told her himself or they might still be "happily" together. I guess it's not really any of my business but it bothers me sometimes.

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+1 y
I decided that the right thing to do was let his girlfriend know. I realize that I should have done this sooner but I guess late is better than never. She deserves to know that her boyfriend is an asshole. I just hope that she doesn't think I'm lying for some reason.
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+1 y
Just to give you a little update on what happened: Also the girlfriend has now blocked me on Facebook without reacting to my message in any other way. I guess I know who she wants to believe. But hey, at least I tried.
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+1 y
Crazy update to this question. Now, a year later, the girlfriend unblocked me on Facebook and asked to know what happened. I guess she decided she might believe me after all.
Should I have told his girlfriend that he cheated?
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