We found it! Yay! My son and I found the hornet's nest, and we weren't even looking for it!
All that it cost us was several stings apiece inside our shirts, as we did a lovely jumping dance, leaping and tearing off our shirts and shouting like wild men. Finding the nest was easy: all I had done was open the metal cabinet on my deck to get out the bag of bird seeds, and Bob's your Uncle!
We were suddenly enveloped in a swarm of outraged yellow jackets; just that easy.
The insects didn't know it, but we were even more outraged than they were, and so I assembled a stinkpot compounded with sulfur, powdered sugar, and saltpeter, and stuffed the mixture into a can with a convenient length of fuse. Then I put on my hazmat suit [flak-jacket] and gloves, and approached the zone of still-alert buzzers flitting about. I lit the fuse and threw the smokebomb into the drawer, shoved it closed and then showed a mighty clean pair of heels: at the quickstep!
Approaching cautiously a few minutes later, I could see thick yellow smoke seeping out of every crack in the cabinet, and a few very despondent hornets buzzing around trying to figure out the horrible disaster which had struck them. Sorry, but they never should have started with me.