Boz, not meaning to slur the good name of the Union soldier but there are many accounts of slaves having their property, humble as it may have been, stolen. Also remember that it doesn't need to be true to find itself into a song, especially if said song were written as what we might call propaganda. Finally I will claim it was just a wild guess and that you know as well as anybody I am perfectly capable of being wrong... in spite of what anybody else says :-)