As far as I am aware, this is the latest about Discover and Invoke cards:
So, the first question would be, did you have Galakrond in your deck? Either originally when you built your deck, or through some “getting cards from other classes” shenanigans? Harder to do for Shaman, I think, but could happen. If you did have Galakrond in your deck, then the Invoke related card would become fair game for Discovery.