“Might explain why “buried treasure” is so seldom found”
Au contraire. SunkenCiv just posts= about yet another cache of buried coins in the UK at least once a week. It seems you can’t turn on your metal detector there without finding another Roman horde in a pasture.
Even the mudlarkers need permits to search for stuff on the Thames. I believe they are required to turn in objects to British Museum for examination. Don’t believe half the metal detecting I see on YouTube. There are a couple I think are real finds. One guy just got 4K at one of the London auctions.