Weres my apprentince in the battle frontier

[Darklugia]

That bug catcher?in the battle tower.thinks if you know what i'm talking about.

Dark۞lugia

[Angelic Kitsune]

Do you mean the trainer that asks you what they should put in their team(etc)?If you are,they show up after you beat a Battle Tower Tournament.After you answer their question,they run off and you must beat another tournament.Your answers influence what pokemon they'll have either as your opponent or partner in the battle tower.
Hope this helps.

[Dragon Lover]

In a more simpler way in the battle frontier where you have to fight double battles. You can also just go to serebii and look there.

~DL~