Oh, now THIS is bizarre!
So, I told you I got it working with the reflash. Well, that was temporary. After transferring back to the EMMC, I opened /etc/network/interfaces to configure my network. I uncommented the line "iface wlan0 inet dhcp" and rebooted. wlan0 was gone! I opened interfaces and re-commented that line, then rebooted...and poof! It was back!
I copied the ap6212 firmware over the brcm firmware like @martinayotte suggested, but wlan0 still is gone.
So....I commented out the entire interfaces file except for the lo lines at the end and tried configuring the wireless using nmtui. That worked!
Bizarro-world. Any idea of what could CAUSE that?