Mushroom Prime Minster card bug

Describe the problem. Be as specific as possible!:
He has his own set of monster cards, even though he can only be fought one. This makes it impossible to obtain all 5 cards.

 Images of problem

None, due to the fact I can't screen shot that when you re-enter the map you can't re fight him.

Describe the problem. Be as specific as possible!:
He has his own set of monster cards, even though he can only be fought one. This makes it impossible to obtain all 5 cards.

 Images of problem

None, due to the fact I can't screen shot that when you re-enter the map you can't re fight him.

Apparently, you can fight him, exit the map without clearing the quest, retry. Saw it somewhere.

Apparently, you can fight him, exit the map without clearing the quest, retry. Saw it somewhere.

But, that's another problem. Who would think to do that the first time you fight him? I never even thought I would fight him. o.o