SpongeBob SquarePants: Underpants Slam (found Xbox Live Arcade game; 2007)
Spongebob Squarepants: Underpants Slam is a 2007 Xbox Live Arcade game released alongside Screwjumper!
It is an action-puzzle game that includes the characters from the Spongebob Squarepants animated show.
Due to a lack of interest, the game's servers are still up but are often empty, and the game is no longer available for sale on the Xbox Live Marketplace.
"Lost" status
This game can be determined not so much as "lost" as it is "inaccessible," because many users have it downloaded on their hard-drives, but it's not currently available to those who don't have it and want it.
As such, this game falls into a special in-between group of lost media, since it wasn't quite lost.
Found Game
After the efforts of users Brodster and SpooferJahk, a downloadable version of the game has been preserved from a torrent link among XBLA torrents, and can be found in the Mega link below.
Download Spongebob Squarepants: Underpants Slam!
("You will need a modified/Jtagged Xbox 360 console to play the game, and I can confirm it works on one." -SpooferJahk)