Received card mastery for a card I drew but never cast

Squirreljester

I just received card mastery for a card I drew in the final round of a match but never got to cast, Volcanic Rambler. I don't know if it counts the cards you draw in some way toward mastery, but I thought it was just cards you cast.

majincob

It counts all the cards in your deck. When you win, all the cards in your deck get some XP until they are mastered.