Too funny!
When paddling, mine is usually the overloaded upstream car- cause I have the 78"-wide rack. The old red/white rig could be left just about anywhere with the keys in it and unlocked. A proper thief would be too embarrassed to be seen in that. New rig is keyless entry - so I can leave the key in that one too, but locked (so long as I remember to turn off the headlights).
I figured out once that you can keep from missing an obscure and unfamiliar take-out by tying a scarf to an overhanging tree at the start of a poling trip. Worked great when I used it. I figure that someday, someone will take the scarf as river-booty......