3DS:Animal Crossing: New Leaf

Animal Crossing: New Leaf is a simulation video game for the Nintendo 3DS. It is the fourth mainline game in the Animal Crossing video game series.

2016 re-release
This game has a re-release in 2016 with the Welcome Amiibo content integrated into the base game. Gameplay-wise both are identical once the updates are installed, but this means that both have a different Title ID.

Sudden missing save in un-updated game
When a save file is upgraded for the "Welcome Amiibo" update, the format of the data is also upgraded. The base game uses the  file, while "Welcome Amiibo" uses.

On an unmodified console, the HOME Menu blocks launching New Leaf if it detects that the save was updated and that the game update is not installed. However Luma3DS removes this check, so it is possible to launch an un-updated game with an upgraded save, leading to it thinking the save is missing.

This can be resolved by installing the update.

Guides

 * /Save editing

Other resources

 * Wikipedia article
 * TCRF page