Maybe you have already tried this, turn everything on, plug something into every outlet top and bottom receptacles. Watch the antenna booster light and anything else that draws power. I had a storage area light I did not know about for months. Flick the switch and look for a change.
If nothing happens, I would take the face plate off and see if it has any wires. As a last resort I would read the voltage between the switch and ground with a volt meter and start pulling circuit breakers of fuses.
That kind of stuff would drive me crazy.