The small pack of cards is the errata for Mistfall.
Stretch goals for Heart of the Mists are a full deck of cards, so you can just count the number of decks and if the total is 7 you're all set.
Of course by time I read this I'd already opened and sorted all the packs. I'm sure I have then all, but I'm no stranger to ks packing mistakes.
Can you name a card or two from the extras so I can confirm?
And thanks for the awesome looking game! I can't wait to get it on the table.