This Article Contains information directly from the Pikmin Games. This article is based off of an Enemy/Treasure/Area/Cave/Pikmin/Character from the Pikmin series of Games.
The Prototype Detector is a device called a 'Love Tester'. It is found on the last (5) sublevel of the Hole of Beasts, and is held by this cave's boss, the Empress Bulblax. When you retrieve this treasure, you'll unlock the Treasure Gauge, a very reliable device that will help you track down every treasure in the game! An Antenna Beetle will mess it up, though.
Being in the Explorer's Friend Series, it is part of the Exploration Kit.