The public and their vehicles

I was walking across the road in front of our garage this morning at around 8.16 am, a woman had parked her car on the garage car park, in appearance in fairness I am dressed in overalls, so the woman walked over to me while I was walking across the road and gave me her keys to her car and said, its booked in for 8.30 am for an mot test. I said to her, do I work at that garage? Have you ever seen me before? I could now just drive off with your car, you have absolutely no idea if I work at that garage, he replied, well I have a good memory for faces, so I said well that does not stop me driving off in your car, and you still have not proved I actually work here at this garage, what about the others across the road there ?