What does the light switch control?

I'm moving into my GF's condo and she has a light switch which does not appear to control anything. I have tested all the outlets with a 3 prong outlet tester and all appear in good working order and do not change when turning on/off the switch. I have tested that the switch and it is hot and receiving current. My next step is to remove the switch and test continuity capacity (i.e. if it is actually turning on and off) once I have found the circuit breaker.......what does this switch control? FYI the building is 6 years old in downtown Chicago and she is the 3 owner. Maybe a overhead "outlet" that has been dry walled over?