Firstly, when you choose a workshop to do work for you, then you obviously trust them with your car.
I do not know you, therefore i would not leave you my car for you to drive it. There have been several members on this forum that i trust with my car and those people have also been given the chance to do laps on the track with my car. Thos members have driven my car further than 2.6km, faster than 80, and have hit the limiter.....Its no big deal....the car was built to do such things.
When a workshop takes your vehicle, they do take responsibility for it.
If it had been hoon lawed then i would be the first to stand behind with support for a thread like this.
If it were damaged, then the shop is responsible for that. It happens...accidents do happen.
If they used the car to drive and pick up some parts then i agree thats a bit of a prick of a thing to do, but i certainly wouldnt have gone to these lengths.
Humour me, can you PM the workshop to me please?