Flirting with a man in a relationship

I work with a guy (both new to the job) and we just so happen to find one another attractive. He begins to talk to me and flirt, gets my number and all. I add him on social media and it shows him and a girl. I asked him, because I didn’t want to be the girl interrupting a relationship and the next day he showed me the messages where they had broken up. We met up the next day at his house to go out and his, now I know, girlfriend showed up and flipped out on me. I don’t know how I feel, but I also know I feel guilty for being that person. I just needed to vent and hope I’m not the only one:(