Obviously the Deke Moffitt version is derivative, yes - but the Henry Thomas version does not have the bridge, or the "chug chugs" or the "toot toot" so I'm guessing those may have been Moffitt's contributions, as well as a modification of the melody. Still, it is not accurate to call the song "Moffitt's composition". If the 1928 version was not composed by Henry Thomas, then it is an old traditional folk song of unknown origin. The Henry Thomas version is the earliest version I could find a recording of, although there are many versions listed in the Roud Folk Song index going back as far as 1892, though most with notably different lyrics and structure. The refrain 'Little red caboose comin' behind the train' appears to be common to all, however.