Microscopic particles don’t tend to sell well on E-bay.
And, at the time, the government got very thoroughly ruthless about any shred of debris.
Brazel being stripped naked and kept in a jail cell for several days while they repeatedly threatened to kill every family member they could track down if he so much as uttered a single revealing word about the whole thing . . . tended to discourage scavengers.
And having an array of troops repeatedly sweep a wide area virtually shoulder to shoulder is a reasonably good way to cleanse an area of even small bits of debris.
I find if you arrange for a dealer to attach the particles to a nice, signed photo of Tony Orlando & Dawn, they sell far better. And it’s no fuss, no muss, too.