Super Monkey Ball Mini (found tie-in Flash game; 2001)
Super Monkey Ball Mini was an online Flash game published by Sega in 2001 to tie in with the GameCube game Super Monkey Ball. It was a rather impressive Flash game at the time, with it featuring 3D courses that could be rotated, with the player tilting these courses to guide AiAi to the goal. The player could choose from 9 levels.
However, the game was eventually taken down around the mid-2000's, making it effectively unplayable. Only the SWF for the menu stub survives, with the rest of the game being lost. This is because rather than storing all of the assets into one SWF file, the game was spread out over several SWFs stored in one location. This included the music, the graphics, and the levels.