Any luck? Could it be a child's memory of one thing (the line from the movie) being filtered through other things that were also there (a lot of folk music) so although you firmly recall a song with that line, there never was one, really? That would bite, it sounds like a fun'n. Do you remember anything else about the circumstances under which you heard it, maybe relatives, who might help with the search? I would love to see the rest of the lyrics.