Recently I have noticed that--while gardening--my Gardening Treasure Cards are able to be viewed normally through the Gardening Tab in the Treasure Card section available while in my house. However, I've noticed that if I were to open my backpack, navigate to the Gardening Treasure Card section, it displays an inaccurate amount of Gardening Treasure Cards I actually have, and therefore cannot browse or delete any. The same goes for trading cards; I can the correct amount I have fine, but alas they are unavailable for me to view in my backpack.
