It sounds like there was a weird saving error going on there or maybe a glitch of some sort. If the game auto-saves, I suggest watching carefully for the saving icon/words to appear. If you manually saved the game (and you're sure you clicked on it), then I am not sure what's wrong and it may be some kind of glitch. Perhaps check the game case/manual and see if there is a support number? Or maybe even just try calling Nintendo Support directly? I'm not sure what to say!