Back in the 1960s, I met a man early one morning walking in an empty Macy's parking lot. I was a cop back then, and since he seemed to be wandering aimlessly back and forth, after watching for a few minutes, I drove over and asked what he was up to. Well, it seems that since he retired a couple of years before, he drives around from state to state. In each large town he ends up in, he goes (went) to the large parking lots early in the morning, before the stores open. Then he would start at the west end of the lot and start walking back and forth watching for any bright flashes of light. Then, keeping his eyes on the spot, he would walk up to it and generally find a nice diamond. (As he said, "a lot of glass too", but you soon learn to tell the difference".) I guess he was telling the truth as he took a round plastic container out of his pocket and showed me a couple of beautiful large diamonds.
I've kept my eyes open anytime I'm walking through a parking lot. Though I haven't found any diamonds, I did find a large CZ in the Sears parking lot. Still worth looking. I told a jeweler friend of mine about this, and he says it's probably true as diamonds are clamped in under slight pressure, and sometimes, all it would take is for a woman (or man) to bump the ring on a door handle, and the diamond could pop out and might land several feet away. So, if they even noticed it pop out, the chances of them finding it among a lot of cars would be very slim.
Eagle