Before I was on POSCON, I was on another network and had a loss of radio connection that I attribute to me physically disconnecting my headphones, thinking that I could revert to the computer's speakers, at least for a little while. Unfortunately, it seems that Windows didn't like me pulling the plug on the headphones, so it caused my sim, (X-Plane 11) to stop seeing the audio driver for the headphones, thus, plugging them back in didn't work, and windows didn't allow me to switch to another device for audio, like the speakers. Hence, I was suddenly lost comm and there was no fixing it short of restarting X-Plane.
So maybe you had a brief disconnect of your audio system.