Just to update, this wasn't a bug. 
  
  
I had not played the App version of the game before, and had never actually seen a card Banishment.  After playing more, I realized the option displays on the right-side of the card when applicable. 
  
I think the original problem was me overlooking the damage was coming from a Bunyip, and therefore not reducible.   
  
  
Thanks for everyone who answered.