Could you substantiate the claim that treasure scrying was commonplace then? It’s not that I seriously doubt your assertion: I just think that elaboration would prove interesting. (Also, I might think that mine salting would be even more popular, not that Arky has claimed otherwise.)
Those wanting an example of fraudulent treasure scrying can look here:
http://oakisland.esolutionswork.com/tiki-index.php?page=Treasure%20Scrying%20Fraud%20Maine%201804