I know at my old work at the brake parts company, the E body rotors we manufactured came with studs and they were right hand threads, so if someone replaced rotors, unless they swapped out the studs for left hand thread on the drivers side new rotor, you were getting right hand.
And I believe it's been a number of years since any of the parts stores like Napa stocked left hand thread, so if a mechanic broke one of the left hand ones on a car, he'd probably replace the whole set with new right hand ones.