I was looking for Dialga and got this MF instead. Holy shit. Is it a coincidence that Pokémon Black is the next game I want next

I used the Master Ball

Just as a note, never use a master ball when a pokeball and many game save point reloads and paralysis or sleep will do the trick. You can catch anything in a pokeball as long as it won't run.

I was just nervous as hell to use up all my Ultra Balls.
Plus, I"m planning on (hopefully) catching Necrozma in a Beast Ball anyways just out of pure spite.

I can understand that.

I traded my Reshiram

Little tip, always stock up on Ultra Balls and have a Pokémon that knows a move that can't faint a Pokémon