Yes, I remove absolutely everything before sending the car to the workshop
Not exactly, I remove the valuable items (cashcard, parking coupons)
No, I drive to the workshop and pass them the keys
Wow, hanky panky with the car parts? AFAIK, some car agents' satellite service stations are actually run by sub-cons. But the agent does control and monitor the service level strictly. For my previous car, some paint on the fender got stripped, probably some corrosive liquid spilled onto it. Very small droplets, but I told the service manager. The manager arranged for my car to be re-sprayed, and gave a free next servicing. So happened the next servicing was a major one, and it was entirely free.
For the current car, from my in-car recording, I could see the mechanics take the car for test drive after each servicing. When I fed back on sounds from the brake, they actually took the car to a deserted car park to test.
polll result is clear - only remove valuable items e.g. cashcards.