That reminds me.
I used to work at RadioShack, and one time, a foreign language speaker conversed openly with their interlocutor about casing the place to try and steal stuff later. I was very fluent in that particular language at the time, and I piped up with “Hey, just be sure to come back after my shift” in their language. They were pretty pissed off that I understood them and left without buying anything. People say the weirdest shit when they think they have privacy.