Not sure what's the detail of this case, but stupid things happens.
back at UVic, I once saw a Mini parked next to me with its key on top of the car.
I grabbed it and handed it to campus security. (he actually took my number and other info).
The second day, a cute sounding chick called me to thank me and wanted to buy me a coffee.
I cannot... yes, up until today, figure why the fuck I said no even when she insisted and I was single and horny like a freaking rabbit...
Back to topic... good luck finding the car. I think it was an amateur job. The guy/chick who found the key most likely took it for a joy-ride.