I reported this problem on test, but it seems to have gone live. Spell cards on some pets are missing. The card space appears as a white box. This seems to be happening on pets that gain cards with level. If the spell has not been unlocked, normally it shows but greyed out until you level up, then as a regular card. Now the greyed version of the card is missing. There's just a white rectangle where the card would be.
Two of the affected pets are Ninja Piggle and Myth Treant. There may be others in my collection that I haven't seen it on because they weren't in inventory like those were.
I reported this problem on test, but it seems to have gone live. Spell cards on some pets are missing. The card space appears as a white box. This seems to be happening on pets that gain cards with level. If the spell has not been unlocked, normally it shows but greyed out until you level up, then as a regular card. Now the greyed version of the card is missing. There's just a white rectangle where the card would be.