Shuichi Saihara, I personally wouldn’t want to advertise the card key to a hotel room on my person, let alone something that identifies me as suspicious in a situation like this. A Monopad is a whole other kettle of fish, because on the surface, it doesn’t look remotely suspicious now, does it? On top of that, Rantaro had yet to even reach the door. Why would he have a key out?

Just because you didn’t see something displayed clearly, doesn’t mean it doesn’t exist; we may not have seen Ouma waving around his Bugvac, but that doesn’t change the fact that he had it.

Besides, a very large assumption being made here is ‘card key holder = game runner’. Even though we know Rantaro wasn’t the ringleader or gamemaster, that doesn’t completely rule out acquisition of this item. Could it be, this was the reason a card key was practically [waved around in your face later]?