Propane bottle exchange, a target for thieves?

It's a lot cheaper to get the bottles refilled instead of exchanged (here in the Heart of America anyway). And with refilling you get a full bottle.

The very rare times I make an exchange I've always left the empty locked up in the car/truck while I go into the store to make the purchase. For that very reason. Then I drive up to the rack, give the clerk the empty, take the not-quite-full exchange and drive off.