Why would non- folkies know " The Last thing on my mind?" .
Was it ever a hit? How often would the song be played on any tv/radio show?
But, every year the Zoo song will be played to countless children. And, sung by countless parents to their kids.
It's not even a close contest.

Just had a thought. Sing "Mamas taking us to the zoo tomorrow" to any stranger in the street and ask them if they know the song.
Then sing the first line of " Last thing..." and ask them if they know that song.

The Zoo song will win hands down.