The problem with O/I, at least how I see it, really there is no concrete proof of something actually there. Yes we can try and piece together who "might" have tread on the island, and what "maybe" they might have brought. But that's it, might and maybe's don't always pan out.
Heck, my farm has a bunch of old deep mines under it, back into the early 1800's some of them. And it has all kinds of springs. So a depression in the land showing up can happen, like when one of the shafts collapses. Someone not from the area, or much later in time, digs down and could easily break into one of the old shafts, or "Ancient Tunnels". Old timbers, maybe some broken tools, torches, trail cart tracks, old coins, trash, and such and it's "evidence" that someone buried something.
And yes The English/French/Indians/Yankees/Rebs/Masons/and KKK/even Slaves have all passed over this part of the state. I saw a UFO there once so it could even be Aliens! So they could have stashed almost anything.
Need a flood tunnel, that's easy enough, screwing around and you break through into one of the springs and it must be something that they built to scare off intruders. You can get pure water or tainted water depending on where you break through.
How did they transport all the treasure? Well it's a 15 minute walk to the river that can take you all the way to the mouth of the Mississippi and the Gulf of Mexico. Or maybe they came from the Atlantic, also not that hard to ferry the stuff down a couple of canals, or pack the goodies in on animals. Or any of the bunch who trampled over this place might have met up with one of the others and had to stash their goodies when they got into a fight.
Skeletons? Who's to say if part of the mine collapsed on somebody, be it some wildcatter, an indian, or some animal that crawled in and died there.
Evil gas that mysteriously kills folks digging for the treasure? Well there is natural gas on the farm, got two wells, so hit a pocket of it or some methane pocket and you'll be just as dead.
What else? Oh, a tree, that might or might not have had a block and tackle attached at one time, well there is a Maple tree that is nearly 6 feet in diameter, and has some low hanging branches that at one time had multiple swings and yep even a block and tackle on it for when we butchered animals. Even has grown around the chain that held the block and tackle. I'd lay money on that tree being around when my family settled the place in the 1700's.
Almost forgot about the signs, carved on trees, and rocks, piles of rocks, bent tree limbs, and so on, got all that there.
Campfires and torches at night, well way back when we didn't have heaters or flashlights, and we did have the Klan who had a thing with using fire. Or maybe it was one of the many folks who still roam the area with their stills and shine out there.
And a lot of the area was strip mined, so everything that might have been there is now all scattered about, just like O/I.
Holy heck,I need to get ahold of the Brothers, just as much chance of finding the lost treasure on my place as they've gotten from all the experts who've led them down multiple paths. And I'd love the money from the TV show in my pocket.
