yep i did that and found the room, but it is dark, i searched every inch and no one was there
i have been to Yureyu building, since i only got luna's dark gym to go
i can only access floors 1-4
i am pretty sure i got the other stickers
1 - The first one you receive in the dept. store = Floors 1 and 2
2 - Save the girl from the Jasper Ward = Floor 3 - REMOVED IN EPISODE 10.5/11
3 - Save the boy from the Drifloon (lol) near Shade's gym, and again in the Jasper Ward = Floor 4/Floor 3 in episode 11
4 - Save the guy from the Railnet = Floor 5/Floor 4 in episode 11
5 - Help the girl with the broken leg in Chrysolia Forest = Floor 6/Floor 5 in episode 11
i started this save in episode 11, so the elevator girl event gift turned to an egg
so the guy in railnet should be the last one, maybe there are some weather/time of day restrictions ??? when i found the room with lot's of aarons above on the bars above, it is almost completely dark after i went down the stairs
there is a door on the top left corner, and a few rocks and cracks, but no guy there