For years I had no idea that one room with key, clams, and rock spike enemies existed. I had no idea for a long time that was underneath the platform in the tower water leveling room. Because of this, I thought I was screwed so I restarted the game the first couple of times I played Ocarina of Time. I literally thought back in the day if you didn't choose wisely on which doors to unlock in that temple you basically softlocked the game.