If someone else wanted that AM allocation, they would have filed a complaint that the licensee was not operating, and the license would be cancelled.
It's also not typical to monitor your own signal directly. You have telemetry coming back from the transmitter site. This includes antenna VSWR which would spike if the antenna disappeared. Or no telemetry at all, if the transmitter building lost power or was raided etc.
There is zero possibility that a compliant licensee would not be aware of an antenna loss within seconds of it happening. So the question becomes what level of noncompliance this licensee was operating under. Sounds to me like they were cheating because AM transmissions are low ROI.