Sounds like a hoax if they can't site where they got their info from. The topography is similar to what is in the journal, problem is there is no mention of crossing the Ohio after they split up at the forks of the Sandy River. Ohio isn't exactly Southwest or West from the Louisa, KY area either? I won't totally poo-poo the possibility, but I find it far fetched. I don't know of any collapsed caves or openings there, although it has been over 20 years since I visited the park and I don't remember. You sure they weren't leading you off the scent at Caney Creek? Same could be said for Clifty Creek S.P. in Indiana? And there are no arches there either...now if the journal is a complete hoax from the get go... any hunch is as good as another. Show me a hole in a mountain this side of the Mississippi River and pull some silver from it...then we are talkin'.
I still think it is most likely with lead, but I am not a geologist. I heard recently that KY has some Platinum tubes in South Central area of the state, they are deep and not worked from what I was told from a U.K. employee.