Do I tell a man's gf we hooked up?

For context I'm a man and I have Herpes. I've had it for 10 years. I ALWAYS tell people if we're going to be intimate. Most people aren't interested, fair enough. I haven't been dating for over 2 years and at a bar I play music at a guy was being incredibly sweet and buying me drinks.. I didn't want to assume his intentions but it became clear he wanted to hookup. Not usually my thing but the attention felt nice.. I walked him to his car and I told him the situation. He just kept saying it didn't matter, it's fine etc. So we did the deed. It wasn't even good honestly. I was embarrassed for him by the time I left. He called me several days later to apologize and confess he has a girlfriend. I got really angry and told him that I'd spare him the shame of finding her but he better never cross me especially with her present because I'd tell her then. I think it's morally wrong to do something like that in the first place but to expose your partner to STD's is just so selfish and horrible and I hate that I am potentially the reason this girl could end up with STD's. I don't think anyone will get anything as I take extreme caution and medications but I'm still extremely angry at him for including me in his miss deeds.

EDIT: thank yall despite having only posted recently I'm going to get to work finding out who she is and contact her. I found his fb but it's pretty tightly locked up so I'm going to be doing some asking around and let her know..