There is a known (and fixed) glitch in earlier versions of the game (version 6+ it is fixed), where you can't find / meet Uzumaki at the Grotto.

There's not much you can do about this if you're playing the free version of the game (as it's several versions behind the latest, which is version 7).

TL DR; if you're experiencing this you will most likely have to wait until version 6 becomes public (next month). Alternatively you can play the latest version now where it's already sorted out.

~  My Big Little Brother