Somewhere in the middle section of floor 2 there is a room with some dark tiles on the northeastern corner. Blow that corner up with bombs to make a hole into the floor and jump down. Then proceed north and you should reach the northern end of the level and floor 2 eventually.
Argh! I knew it was going to be something as simple as that! Blast it! I bombed every wall in that room and tried using the whistle on those tiles! -_- Blast it!
Thanks for the help.