I haven't bought a car in years, recently took a test drive and was surprised by the way they're doing things these days:

It wouldnt be hard to find you if you were not who you way you are. All they would have to do is follow the trail of tildes you leave behind you. You cant get away with anything. 

It's cheaper to do that than renting a car to do a few errands. Did you at least buy the car or did you just leave it somewhere when you ran out of gas?

"Key fob trackers for under $100."

I think it depends on the sales person or the dealership. I have bought a few new cars over the years and I have either had the salesman ride along or had to leave my actual driver's license (not a copy) at the dealership.  I think a good sales person would ride along to point out the features and keep up the sales pitch, but in my experience a lot of them just want to sit there and wait for someone to buy a car as though they are buying tomatoes at the supermarket.

You actually gave him your real phone number??   Boy are you going to get a lot of robo calls.   They resell those numbers to make up for all the cars that don't come back.

Ever notice that they only have a few gallons of gas in those cars?  It's cheaper just to buy the car than fill the tank up.

i dont have a car

It’s a safety thing a lot of them do now. Better to lose a car than have a salesman die. Odds are, they were tracking the car anyway. If you took it, you wouldn’t get far.