I think I stumbled onto a solution for my own problem.
I recorded a 2-hour video for a customer using a wireless cavalier mic with an Apple 3.5mm to lightning adapter. No audio was recorded on the video (even though my headphones, connected to the receiving unit indicated 100% sound).
It seems the Apple adapter cable is for TRS to lightning; the external audio required TRRS to lightning.
I'm posting this in the hopes that someone will save a lot of stress having to experience this for themselves.
Can someone confirm this theory?