They'd probably leave and then go file a theft case with the cops. The way I heard TYer describe the encounter is that they claimed ownership of the "product", explaining they considered it stolen without making an accusation, and then asked for it back.

It's kind of like, if your bike was stolen. At least once upon a time. And you saw it in front of someone's house, well you'd go to their door probably and ask for it back. They might just give it back to ya.