[muawiyah]

Right, sure ~ you leave your car in the parking lot. I go over, bust the window, open the door, jack the engine, and give you a call on your 3G device you left plugged in to charge while you were at the bar.

You say "Oh, yeah, sure, you took my car while my back was turned. I'd rather collect on the insurance"

Which is pretty much what I think you'd say after a couple of beers anyway.

That still doesn't give me a good title to your car. Something else is required.

[SmokingJoe]

Right, sure ~ you leave your car in the parking lot

Nice try.
Now why don't we just take that further?
You leave your car in parking lot, you pay for use of the parking lot. Your car is under the protection of the guys that run the parking lot. If someone takes your car from that parking lot, that is theft.
On the other hand, you drop a $50 note on the street, someone comes along and sees it and picks it up, that is NOT theft. If the guy tries to return the money, and the alleged ownder refuses to take the money back, it becomes abandoned property, and the money reverts to the guy that found the money.
Get it?