While I do believe that if anything was buried there it’s gone now, that doesn’t give us the answers to the more interesting questions of “who?” and “why?”
It’s also not a “secret” as defined here.
I’d like to know the truth of whether there is/was a Loch Ness monster, Bigfoot, or whether alien spacecraft have visited the Earth.
You know, you have a point. Other than Hoffa (and those who knew might all be dead), is there anything here which is a “secret” in the way the OP phrases it?
thursday next, brings up this “The mystery of how the Church of $cientology became tax exempt” and that’s an interesting one, as it was a secret Appeals settlement at the very highest level’s. Some of the details of the large amounts were made public, but the whole thing has never come out.
What I want to know is: What are women really thinking when they refuse to tell you? Also, on our current salaries and with our currrent bodies, how do we make our wives Truly and Completely Happy*?
*without divorce
Honestly, it’s not like I have a hard and fast line. I mean, Jack the Ripper probably used to be a secret, but now I think it’s a mystery, barring discovery of some miracle evidence. Lots of things that were secrets become mysteries if they remain unrevealed.
Here’s one that absolutely meets the OP’s secret standards:
Where is Osama bin Laden?
He shares an townhouse with Elvis and the Loch Ness Monster somewhere in… I’m sorry, did I just say that out loud? Forget I said anything. 
Hasn’t this been more or less revealed by dozens of sources at this point?
It was mainly Iraqi ex-patriot/defector fairy tales on one hand, and very little hard evidence of anything concrete on te other. Saddam had done such a good job of faking everyone out, that anything questionable (metal tubes etc) was assumed to be defacto “slam dunk” evidence of WMDs.
Duh!
The whereabouts of Lord Lucan?
Shergar?
Who commissioned the Georgia Guidestones and why?
The hidden theme of Elgar’s Enigma Variations.
Of course, Walloon is right on this, and hh has to eat crow. I wanted to describe the book as the garbage that I saw it and tried to get by using somebody else’s description of his travesty. Most well researched books are little more than lawyer’s briefs (or some derivation of same)
'Tany rate, *CC * is tripe.
Yours,
hh
Seven!
Also, there seems to be solid evidence that Saddam was planning to restart his WMD programs as soon as the UN sanctions were lifted. The “defector fairy tales” probably convinced Bush that Saddam had decided not to wait. And that was an idea that Bush really wanted to believe.
My guess: Denying tax-exempt status to a self-described “church” that could afford a lot of good lawyers was a can of worms the IRS finally decided it would be better to leave unopened . . . as the very idea that might happen might really piss off certain much better-funded and better-organized and more widely respected groups.
Do the Beale ciphers describe the location of a hidden treasure?
Did Melvin Dummar really pick up Howard Hughes in the middle of the Nevada desert?
Did Floyd Landis really intentionally dope himself up for this year’s Tour de France?
Granted, this isn’t exactly an old mystery, and it may soon be resolved . . . but still.
Well, Lance Bass’s sexuality is a secret no longer. That had to be one of the biggies.