My UMass passengers last week brought it up more than once. When it has, I have made sure to mention several ways to be sure you're getting into the car you've meant to and, of course, that someone just saying they're a driver (when you haven't requested one) is no different than taking a ride from any other complete stranger.
Thankfully this wasn't worse and they were able to find him.
Since the kids came back to school (before that incident) I've notice more and more of them reading my license plate before getting into my car I try to remember to complement them on it in hopes it remains a good habit with them. One can never be too safe.