headlight comes on when blow horn

Hello,
Have a coworker with a 2002 Honda CRV..interesting problem.
Just replaced left side headlight cause it was out. A couple of days later, he realizes the right one is out too. He is driving around, blows the horn for some reason and realizes that the headlight now comes on. It is intermittent. He said he has witnessed this on two occasions. Tonight he went out to grab something to eat, and he said all worked normally.
Any ideas?
Thanks!

Grounding issue I would guess. Possible loose connection.

Not sure of the exact circuit...But in most cases with a 2 filament single bulb system it will be supplied with voltage at the terminal common to both filaments and the grounding of one of the other 2 terminals will turn on the high or low beam filaments.

Grounding issue I would guess. Possible loose connection.

Not sure of the exact circuit...But in most cases with a 2 filament single bulb system it will be supplied with voltage at the terminal common to both filaments and the grounding of one of the other 2 terminals will turn on the high or low beam filaments.

Thanks!
Yeah, I did mention a ground/circuit issue and that this will involve chasing down wiring.