I'm playing on random seed B7H7G9T7 with plasma deck on white stake (Ante 10, round 20) and I wanted to demonstrate a mate of mine, who just purchased the game, how to try and guesstimate the face down card's value by flipping the sorting back and forth.
For this I intended to make 2 screenshots: one with sorting by rank, one with sorting by suit.
To my surprise, after I pressed F12 (default screenshot button on steam) I was given a screenshot in which the face down card was actually displayed unhidden.
I tried once again, and now it was correct, but it's weird that it happened once in the first place.
I guess it's not an exploit, since it's apparently not readily reproducable. I don't know if a specific timing or luck is involved, but I figured I'd make a bug report as I hadn't found a thread about this when I scrolled back about 2 weeks' worth of posts.