I just tested out the card in the world set and it seems to work fine, but I get why it can be easy to miss. There's only 2 of them you can access right now, and both of them are in the lighthouse if that helps!
Also, there's definitely some issues with the spawn rates to get the 2nd fog card, another player noticed the same thing, and I never tested spawn rates for my spawning system, just that everything seemed to spawn at all, so I might need to tweak that a bit.
I'll likely be adding some sorta card hints as well, cause all cards existing should be attainable after all, but some of them aren't very clear which isn't great.
Also thanks! Glad you've enjoyed it so far!