> It is hard to imagine the FCC wouldn’t notice that there was no signal on that AM station for that amount of time, or the owner, or the power company.

Maybe the typical approach of having flaky monitoring and after enough time, you simply chalk it up to "well, seems the monitoring is offline again, but no one is complaining so probably the thing still works"?

Alternatively, the owner did notice it was missing, but reporting it as missing would also mean they have to shut down FM service, so they left it until someone complained/noticed.