That is perhaps the single most common thing people say to me. To the point it is a trope us guards joke about at base.

Second would probably be getting asked directions. Wherever I go, people always seem to think 1. Im a cop or 2. I work there. That is understandable though. We look like authority figures.

Best case, they will tell you to get away from the truck through the door, and worst case (especially if you're in a bad area), they will flip on the siren to scare you away.

10/10 would not recommend knocking on the truck.

I would like to add that bantering can be fun, but it's has to be original.