I leave mine in the wheel well in front of the passenger jump seat with a tote box on top of the blade when I punch out at night. It is still there when I punch in the following morning.
Best case. Or a combo lock so you could just give him the code. Had to cut the chain on a guys hand truck once because I was using his car on a special volume day. Cut one link so he could unlock his lock and reuse his chain the next time he came to work. No idea who the driver was.