It took us a week, but we finally found the culprit in the case of the disappearing Saint Card : the card itself!
Turns out the Red Saint card was slowly drifting off the game map over time and if players took more than 7-8 minutes finding it, it would disappear through the outer walls of the game space.
Pictured here are two cards, one new to check position, and the original card, slowly phasing through the wall, probably to attempt to escape the dark reality we put it in.
List of changes for build 1.1.2 :
-Activated VSync for every graphical quality level, so as to not make your PCs blow too much wind with their fans
-Fixed the drifting game objects issue
You might have to uninstall the game and reinstall it from your Steam App to play the corrected updated version.
Also, if your antivirus is triggered when attempting to launch the game, fear not! Since we reverted back to Unity 2017, this is an old issue where specific files are quarantined, but it's a false flag. Please create necessary exceptions within your antivirus software in order to launch the game.
For more information on this specific situation, please read Steam's Official Support Page about antivirus interference.