it sounds like you have to be in a public lobby first, then hop into private for them to get your id. Can they get your id without ever being in the lobby or any contact at all?

This is not true, if you knew a persons social-club username you could search for the ID associated with it. I can’t find many tools online except for this one no idea of this works or not, I’m sure there are guides to obtain R*ID’s elsewhere.