Giac, you may well be correct. I found myself humming "My Old Kentucky Home" as I copied these songs from American Memory, Library of Congress. It was a very common practice for publishers to profit from popular songs by others; they would get some musician to make up new words and a slightly different tune and sell the result as original. Collections of old broadsides and sheet music show that this happened over and over.
In the case of "Cabin on the Mississippi Shore," this copy? became popular in its own right.
You probably realize that the version of "My Old Kentucky Home" as you have posted it is not the original version by Stephen Foster.