Having participated in some practical jokes of a similar vein...it could be that three guys (McGinnis, Vaughn, Smith) just decided to "pull a fast one" on some friends, and dug a hole in a secluded spot, and told others they believed they had found a treasure-burying site - but they hadn't found it yet...it's STILL THERE!!!
After all:
1. It is only THEIR word that there was a "depression" in the ground under a tree limb;
2 It is only THEIR word that this tree limb had a block and tackle hanging from it (or a worn spot on the limb, or just a length of rope, depending on which version);
3. It is only THEIR word they dug 30 feet down, finding log platforms, and a "layer of flagstones";
I use the term "their words" rather vicariously, as these stories are ATTRIBUTED to McGinnis and his companions, but there are in fact, NO first-hand accounts by any of the story originators - which even stories don't agree on. The original story told by Vaughn (FIRST described in 1862, 60+ years "after the facts"), had McGinnis finding the "depression" ALONE, in 1799, while searching for a building lot. The current (TV) story has him with the two others, finding it in 1795 while on a fishing trip.
Subsequent searchers acted on such nebulous and enigmatic clues, and rather than suffering public humiliation by admitting they were duped, spending thousands (later MILLIONS) of dollars in a fruitless search based on what amounts to a "pub story" (or "sea story*" for you veterans), the searchers would "keep the legend alive" by admitting only that "they didn't find it YET".
Henry Bowdoin, the leader of the 1909 Oak Island treasure search in which FDR participated in (Old Gold Salvage Group), wrote an article for
Collier's National Weekly Magazine after the conclusion of his treasure hunt: "
My experience proved to me that there was not, and never was, a buried treasure on Oak Island. The mystery is solved." (H. L. Bowdoin, “Solving the Mystery of Oak Island,”
Colliers, August 19, 1911, pgs.19-20.) The complete 1911
Colliers article Bowdoin wrote can be seen here, in which he itemizes the many factual findings which led him to this conclusion:
http://www.jasoncolavito.com/solving-oak-island.html
* Fairy Tale begins: "Once upon a time..."
Sea Story begins: "I sh*t you not; this really happened..."
Other than that, there is NO DIFFERENCE.