Diancie's ability did not work?

Dadandi22

I was playing a zoroark deck and had diancie in the active. My opponent was playing miraidon and had it in the active. They were able to play a boss and bring up my zoroark. Obviously a bug because Diancie's ability should prevent this.

DoubleCure

The Pokemon they used the boss on was a basic or evolution (witch zoroark)?

Diancie's ability prevents Supporter card effects done to your Benched Basic Pokémon

Dadandi22

Thank you. My fault, should read the card a little closer next time. Thanks again