If you catch meinshao, it should pop up provided you have everyone in the area except meinshao and audino. If it doesn't, then you have a problem.
On that same note, catching meinshao is the worst. You have to wait for it to sparkle, because the whole time it smokes its immune to attacks because of detect. Unless you have something with gutsy++ and feint or something strange like that.
I did catch Mienshao, and I have everything except Audino from the Diamond Balloon and it says "Complete".
EDIT: Got the Fairy Balloon. That didn't take as long as I thought, mainly through a combination of SRing for Diamonds from saved Miis, using Play Coins to invite more Miis, and getting my hands on a 1717 Dialga which helped me beat more Challenges (I was stuck on the Dragon Marshal Face-Off mission). I went to Flowery Wooded Dell and caught Cherubi, Cherrim, Vullaby, Espurr, and Meowstic.
Rank: 53
Captured Species: 456
Strongest Pokemon: 1731 Greedy+ Lugia
Balloon Progress:
[SPOIL]Leafy Balloon: Complete
Dew Balloon: Complete
Ember Balloon: Complete
Ruby Balloon: Complete
Sapphire Balloon: Complete
Gold Balloon: Complete
Silver Balloon: Complete
Diamond Balloon: Complete
Pearl Balloon: Complete
Black Balloon: Complete
White Balloon: Complete
Fairy Balloon: Missing Diglett, Dugtrio, Cacturne, Hippowdon, Lillipup, Herdier, Stoutland, Mandibuzz, Baltoy, Claydol, Chimecho, Archen, Archeops, Solosis, Onix, Steelix, Regirock, Sigilyph, Tyrunt, Tyrantrum, Caterpie, Metapod, Butterfree, Plusle, Drifloon, Drifblim, Audino, Slurpuff, Xerneas, Feraligatr, Lumineon, Swanna.
Next balloon purchase:
Dark Balloon (1/90)[/SPOIL]