"Burn it to the Ground!" scenario and the number of Gasoline cards

[zombies are food]

Hello! First post on the forums.

Yesterday I was playing the "Burn it to the Ground!" scenario from Growing Hunger, and my heroes had gotten 3 Gasoline cards. After a long while looking for the fourth, I'd finally gotten a Scenario Item Search card, and looking through the deck, I found that there were no other Gasoline cards (4 are required to win the "Burn it to the Ground!" scenario).

My Hero Deck has all 85 cards from the basic, advanced and Growing Hunger sets (I counted them after this occured). But I only have 3 Gasoline cards in the deck.

Did I get a faulty copy of the game, or a faulty copy of the Growing Hunger expansion? How many Gasoline cards are you supposed to have in the Hero deck with the advanced and Growing Hunger cards included?

Was the scenario designed to only be winnable by getting a card that allows you to pick up from the discard pile (meaning you would have to make at least 2 trips into the Manor)? If that's true, it makes the Zombie deck cards that allow them to remove a card permanently from the discard pile incredibly powerful.

Thanks for your time.