"When I drop anything off for any kind of work I record either the odometer reading, or hour meter reading.
When I pick it up I again record those numbers."
I always hate to make a scene because you never know what gets done to a customer's vehicle, when the tech feels he was singled out & when the customer isn't around.
Still, it does happen & all you have is 'Goodwill' that the dealer has your best interests at heart