Where is the Bulb-Out Warning Sensor?

Have high beams, no low beams. My switching relay works perfectly. It switches between the red (high beam) and gray (low beam) wires. Zero ohms on both paths, 12.6 volts on either wire when it is activated by the switching relay. Opened it up just to see how it works. All contacts look fine.

The gray wire goes from the relay to the bulb-out warning sensor, and from there to the low beams.

That leaves two possibilities:
1) a failure in or around the bulb out sensor
2) both low beams burned out simultaneously

I have not yet checked #2 because it seemed so unlikely, but I will check it while I wait for a response to this post.

CLUE - I replaced the radio on Saturday. If the bulb out sensor is in the center console area, I may have disturbed it or its ground.

Thanks!!