You can get a Vulpix with Drought in the forest area of the Dream World after getting 10,000 points. It's been available since the start, so that shouldn't give you any problem. If you are having a problem, check for Sky Drop on your Pokemon, or Chatter, and if you don't have either of those, list your Pokemon here and we'll see if we can help you out.
I have some hacked in Pokemons through AR since I can't get my older pokemons from platinum via an emulator. The first 1 was infernape. I EV trained him and he has some max IVs. I didn't have any trouble with him online. Today, I hacked in a Charmander and Magmortar+ the Drought Ninetales. I am pretty sure one of them or all of them are the one who gave me the issue. Honestly, the reason I hacked them in is because of a friend of mine...long story, but I don't intend to use them in official online battles.
I'll leave you with the Info of the Pokemons:
-Charmander: Hacked in @lvl 10, like any hacked pkmn, i caught him in grass. I EV trained him for spA and Speed. he is @lvl 100 now.
-Ninetales: Hacked in @lvl 90 with Drought, EV trained for Speed and partially spA for now. Some maxed out IVs.
-Magmortar: Hacked in @lvl 100! Normal Ability, Maxed EV @ HP AND spA.
Could hacking them at a high level give me trouble like that? Please note that my Infernape never had trouble and nor did my garchomp.... that's probably because I trained them fairly from scratch when they were a Chimchar and Gible..
If u need any other info, Just tell me...