I've never had that experience, but have come close a few times, only hindered by my shyness uncertainty. One was the two guys who delivered my refrigerator, the one guy went back to the truck while the other guy and I flipped the refrigerator door around and I'd swear he was pushing his crotch into my hand. The other was an electrician working on lights and I helped steady him on the ladder, didn't quite hold him by the crotch.
A friend seemed expert at this, a cable guy 'forgot' a piece of his equipment and came back after hours to retrieve it ... and get a blowjob.