i doubt it would be a kid buying it with the amount of money it would cost to buy it after the auction is over
I think if someone had sold it on ebay, a sale that major would become general knowledge.
It would be far more likely that if anyone had gone to the trouble of digging lots of holes
until they did find it, I think they'd keep it (and I'd guess keep quiet about it)
Another possibility would be that it had been dug up & discarded by mistake for whatever
reason (such as by a utility company like laying down water or electric mains who didn't
know what it was.