Audio Waypoint Recording Channel?

I have an observation that I'm not able to thoroughly test. It might be an area for improvement, but I submit it for your review.

I paired a bluetooth headset with my phone via the Android menu, and it works normally. Within Locus, I began recording a track and then added a waypoint with an audio attachment. I walked a few feet away, and spoke in a normal tone of voice the entire time.

When I replayed the recording, I heard my voice fade into the background. I believe this indicates that the audio was recorded through the phone's microphone, and not the bluetooth headset's microphone. The audio did not "drop out" as though the bluetooth conection had been lost.

Is there a way to select which audio recording channel or device to use? Should I continue testing in some way to determine which device is used when, perhaps, a wired headset is connected?

If the functionality does not exist to choose the recording device, is it possible to add it natively, provide it via settings or a "helper app," or is it a limitation of the Android platform?