It was their (dealers) fault in any case, probably for reasons they aren't going to tell.
Exactly.
At most US dealerships the test drive after service, if they go on one at all, is a drive from the service area to customer parking, or a drive around the block. At my dealer in Germany, the test drive is a 15 minute drive, followed by a thorough visual inspection, with the car going back up on the lift. A master tech performs the test drive and final inspection, and he has to sign off before handing the car back to the customer.