Harmonica of Destiny

I am stuck on the "hit the monkey to make him drop Harmonica of Destiny" part - I have hit him and hit him - keep using up all my energy and he keeps jumping from post to post...now, he disappeared! I've gone back to LaFeet's Cave and then back to where he is, 8-10 times -- I hear monkey noises, but no monkey!! Is there a glitch in the game!?! I have had other fleeting issues in this game, but this one won't go away!! If anyone has any ideas or has solved the same problem, I'd appreciate tips!! Thanks!