Somehow I had missed the entire process, only to happen upon an abandoned nest and a bunch of webbing. As spider webs are somewhat ephemeral, I suspect they had just finished eating all the hornets, and moved on when the food supply ran out. Thanks, spiders!
One day I came home to find that one of the bushes at the end of my driveway looked funny. Almost as if its color had turned more pale. When the light caught it, it looked like it was shiny too. So once I parked, I had a closer look. The entire bush was covered with silk. That was odd. So I kept examining it, and then realized it also contained a huge hornet nest approximately the size of a basketball. But there were no hornets around. The nest was empty. Then I understood what had probably happened. Some spider had found the bush, set up a web, and caught a hornet. So she stayed there, nabbing hornet after hornet, having plenty of nice meals. And, like tribbles, if you feed a spider, you get more spiders. I'm guessing that some of her family hung around and also set up shop, enjoying the constant stream of food, eventually covering the entire bush with their webs. As more and more spiders accumulated, the process would accelerate, the hornets being consumed faster and faster.