I had a similar problem with invisible cards in my ranked historic match. In game 2 my opponent mulliganed to 4 based on the graphic showing when I mouse over their library, but visually it showed them with 5 cards plus their companion with a gap between cards 2 and 3. Then in game 3 my opening hand contained an invisible card that I could only see what it was by right clicking where it was supposed to be. It seemed I could sort of interact with it, but then when I tried to cast it by double clicking it my mana was spent and nothing happened.
I had a similar problem with invisible cards in my ranked historic match. In game 2 my opponent mulliganed to 4 based on the graphic showing when I mouse over their library, but visually it showed them with 5 cards plus their companion with a gap between cards 2 and 3. Then in game 3 my opening hand contained an invisible card that I could only see what it was by right clicking where it was supposed to be. It seemed I could sort of interact with it, but then when I tried to cast it by double clicking it my mana was spent and nothing happened.