They probably didn't get saved. The place I worked for recycled all their plates, and some were used as dustpans as they could get under the paper scraps. There was no need to save them as a new plate could always be made from the masks. When the Hunts tried to corner the silver market many of those got recycled too.
Sometimes they'd get used outside the shop. One guy used them to cover holes in his car. And the larger ones made a nice roof for a doghouse
Most of the 62s we see probably came from someones leftovers from some project at home, or were rescued by the recycling guy.
Steve B