<human>: About an hour ago some guy texted me that I should "keep an eye" on my girlfriend. His number is from California and my girlfriend and I live on the east cost. I was confused and thought he was pranking me and so I asked him what my girlfriends name is. He said her full name. I was creeped out and I couldn't text my girlfriend cause she usually goes to sleep around ten. He makes it seem like she's cheating on me but he won't tell me any information and keeps telling me to talk to my girlfriend about it. I trust her and I don't think she'd do anything to hurt me. How do I approach my girlfriend about this and is he legally obliged to give me his name? I was creeped out when he called me by my name in a friendly way and he kept describing himself as a "concerned bystander".

Can you give me the gist of the text in a nutshell?
<bot>: I got messaged my a random number that I should talk to my girlfriend and I don't know what to say to my girlfriend.