This slip up occurs in the final 15 minutes of the movie. The conference is being held in the Chicago Hilton Towers conference room. It says so on the bulletin board as Kimball walks in and on the podium that the doctor is speaking at. However, when they are chasing each other in the laundry room, you can clearly see stenciled on several of the laundry bins Palmer House, which is a totally separate hotel and a few miles down the street from the Chicago Hilton. It' looks to me like the Palmer House had a more filmable laundry room than the Hilton, so they used that instead. However, they forgot to remove the Palmer House laundry bins!