Not sure where to post this question, but here it goes.
So this is what happened...
As I claimed my Mew from the Poké Ball Plus, I thought I could maybe reset for a better nature, so I restarted the game. When I got back on the game, Mew was already in the box (guess it saved as soon as it was received), but then I noticed it's Pokédex entry was not saved.
Does anyone have any idea of how I can get that entry again? Out of curiosity, has this happened to anyone else?