no way of telling how things end up where they do,i found a 1857 penny on an archaic site once,just happened to be lost on a site,kids lose alot of things over the years,could have been kids camping out and they lost some marbles,i know when i was a kid we made forts out in the woods ,if some one took a metal detector out to some of the fort sites they would probably find old money and some glass marbles,we shot them out of slingshots,now if we happened to build our forts on a prehistoric site there might be arrowheads also