The way I see it, that car ain't moving unless it's towed. You have to call police and they will ticket/tow it.
As far as mesira:
If someone breaks into your house, do you call your LOR or the police? In other words you have a issue that only the police could remove, you don't even know if the guy is Jewish, and by now he definitely expects it to have been towed if not worse, so that was his plan as well