I thought I had saved the game when I played last time, but when I resume the game, the save data is gone. Is it broken?

There is a possibility that the save data is corrupted.

If the save data is corrupted, the system will try to restore it, but if it cannot be restored, the corrupted data will be automatically deleted and the game will be restarted. In that case, the data saved up until that point will be deleted.