With Old-Time rhymes I'm not surprised even if I also find it strange with "Sam". I have only what I did hear when slowing the file down and Molsky's mentioning it (I didn't have the line "Rocky Road, Cindy" before that concert either). When searching through the American Songbag, I came to think that "Sam" maybe refers to someone or something.
Have you been able to hear what Earl Johnson is saying in the last verse?