Oh gawd. . . Okay, this is rather embarrassing. XD
It was in Skyward Sword, on the first official dungeon. I was looking around for some switch to open up a door in one of the first rooms. It took me around five hours to find something that was literally just beneath my feet.
I would've gone and got a game guide or something, but I have a major fanboy rule against using guides in my two favorite series. (Being Kingdom Hearts and Zelda)
The original Zelda was just pure hell for me, it took me about 20 days to finish without a guide. . . >-<