It's a MEMS microphone: silicon electromechanical device + amplifier in one package.

First, this generally means that when depowered, the output signal line is connected to ground by the ESD protection path.

Second, the actual mechanism which picks up the audio is generally variably capacitive-- a few picofarads-- in MEMS mics, and requires a pretty high bias (~15-200V) voltage to induce a usable signal for the in-package amplifier to be able to pick up the audio.

To not only have the in-package amplifier turned off, but also no significant bias voltage across the microphone electrodes, and somehow pick this up on the other side of the trace would be somewhat miraculous.