there are quite other possibilities... Ken hiding in with Yukiko's room Yosuke's room... same goes for Mitsuru
Again, Yukiko pointed out her and Chie had plenty of space, so I doubt they already had Ken in there before taking Rei. Plus, the other rooms are all separated by gender. I am not saying the possibility isn't there, but I am going by what's most logical.
Plus, Yosuke wouldn't open up for anyone. (I guess Yu would have been an exception.)












