Board Game Arena

In game http://en.boardgamearena.com/#!table?table=12258033, around move 64, I wanted to summon Fire Elemental, but when I attempted to place the piece, the status line said I would have to pick up a piece... and offered me no way to do it that I could see. My undo doesn't even appear in the game replay! (I tried clicking on the piece I wanted to pick up.)

I *think* the printed rules would have allowed me to pick up a legend and place it as the Fire Elemental, but maybe not. I am curious what should have happened, and whether there was a UI element I didn't notice.

When you can pick a piece you're prompted to do so and the pickable pieces are lit in white.

In this case no piece was usable because the 3 of them were part of the pattern for the Fire Elemental, and the rules disallow you to recycle them.

That was the part I didn't know-- that pieces used in a summoning can't be the ones picked up. Thanks!