Lighter wrote:
A still earlier text of "Confession of Francis Sylvus [sic]" - all fifteen stanzas of it - appeared in The Intelligencer (Statesville, N.C.), May 13, 1872.

Daniel W. Patterson's A Tree Accursed: Bobby McMillon and Stories of Frankie Silver claims to have seen a manuscript copy of the text from 1865. I can't prove or disprove this, but if the song didn't exist by then, it's not likely it would have come into existence after that. :-)

But there really isn't much we can say with certainty about that case. Records are almost non-existent, and literacy in that part of North Carolina circa 1830 was extremely low.