Presumably the power was on—else the FM translator would've been in violation if it was transmitting. Also the owner never mentioned any monitoring of the AM si

Presumably the power was on—else the FM translator would've been in violation if it was transmitting. Also the owner never mentioned any monitoring of the AM signal, but most radio stations have at least one if not two or three different means to monitor their signals (and the FM is supposed to be integrated into that since it's not its own station). If the tower disappeared overnight... it would not be able to be done without a trace, and if any listeners were listening, for almost any station I've heard of, at least one listener would call into the station.