Actually, Joker makes a reference to it in one of his comment box letters, noting that Nash sometimes calls him Wan. But yeah, there's no dialogue or anything relating to it in the plot.
As for the end of Chapter 3, yeah, it's a tiny bit of a plot hole, but presumably after each character disappears, the rest of their party heads back to Chisha village after fruitlessly trying to get through the portal. Considering the shortness of time between each one's arrival though, it would seem highly unlikely for the various parties to not overlap at all. One could also wonder how Sana gets into the room ahead of both Chris and Hugo.