Lost Lost Treasure is a location-based challenge in Captain Scarlett and Her Pirate's Booty. To perform this challenge in The Leviathan's Lair, it is required to find the super-secret area inside the Lost Treasure room. It is worth 4 Badass Rank.
The hidden chamber, and the treasure it holds is only accessible while either X Marks The Spot or Treasure of The Sands mission is active, and even then it can only be visited once. The chamber holding the lost lost treasure is located on the southern side of the pyramid, second layer from the base - see the [Map].