Empty box appears when opponent plays Cartographer

[Dwedit]

When an opponent plays Cartographer, there's an empty selection box for which cards to discard or put back.

[tufftaeh]

That's intentional to visualize that your opponent does a selection from cards you cannot see.

[Watno]

While it is true that the box is intentional, it is not intentionally empty.

There will be card backs showing in this box at some point in the future.

[tufftaeh]

Oops, sorry, that's even better. :)

[Cave-O-Sapien]

I've noticed the same thing with Sentry, I believe.