If this is true, why are they not in a museum, and why have I never read about them (not that I was shut out or anything, I'm just a big history fan and thought I might have run across a mention)
They being what...the papers the guy (?) say's his family has (& the others)? Well, it's really not reasonable to think that the gov't or some museum has 100% of every single document written by the founders.
Have a look here for but one fairly recent example:
Letters of Delegates to Congress: Volume 25 March 1, 1788-December 31, 1789http://memory.loc.gov/cgi-bin/query/r?ammem/hlaw:@field(DOCID+@lit(dg025422))
Secret Committee Contract
"MS (Privately owned original, 1993). In the hand of Roger Sherman.
1 A copy of a 60-page notebook in the hand of Connecticut delegate Roger Sherman was made available for use in this supplement by Mr. Joseph Rubenfine of West Palm Beach, Fla. It contains 24 pages of notes on Sherman's readings from Emmerich Vattel and the Bishop of Bristol, various personal expense accounts from 1781 to 1784, and copies of reports now in the PCC on Continental expenses and indebtedness, battle casualties, and the hospital establishment as of July 23, 1781, of which only the present notes do not duplicate information available elsewhere."
So yes, there very well could be many documents that remain in private collections and therefore out of the public realm.
If the docs do exist, it would be fascinating to have them (or some portion at least) be made available to the public.