Sometimes, while dungeoneering, I find an item that I already have infinite of. Invariably, this turns out to be a cursed item that simply isn't revealed. However, it doesn't have the usual "?" symbol for an unrevealed item; it looks identical to a safe, revealed infinite item, except for the detail that it doesn't merge with the other infinite items when I get back to camp.
I'm pretty sure this is unintended.