Lost Key

The Lost Key might at first seem to be a treasure, but this object is used differently. It acts like a challenge mode key would in Pikmin 2. In other words, if you can't find the way down to the next floor, you need a Lost Key. When the Research Pod hauls it up in the tractor beam, the next floor's entrance will appear! However, the Lost Key will vanish from the hull as soon as it is gathered. So in that regard, this mysterious item is not a treasure. It has no monetary value. Also, it looks just like "The Key" from Pikmin 2. Because the Lost Keys keep vanishing, it is possible that you're simply finding the same key over and over again. The Lost Key becomes extremely annoying towards the end of the game because of its frequent appearances in hard-to-reach places. You'll wish it could just stay lost. It first appears in the Serpent Garden, part of the dungeon's purpose is to teach you about the Lost Key.

Portal- Kombat  *Sysop*