Well, bummer... I noticed a dearth of activity in front of this hive, (see video below) so I opened it up. Found a bunch of dead bees on the bottom board, right near the entrance--- which indicates a fight to the death for the hive. I pulled the comb, and yellow-jackets were all over it, including a bunch of dead ones.
This hive probably absconded in the face of an overwhelming attack by yellow-jackets. I had placed a YJ trap near the hive and caught a bunch about a week ago, but I must have been too late. Damn.
I pulled the hive apart, cleaned it and stored it. I kept the comb (it had been robbed of pretty much all the honey) to use as bait in "swarm traps" next year. Swarm traps are simply empty hives with some comb in them, and a drop or two of lemongrass oil to attract the scout bees during swarm season. The idea is to tempt a swarm into setting up home in your hive, saving you the effort of actually catching 'em!
Learned some good lessons about preventing robbing frenzies and yj raids in the future.
1. When removing comb from the original hive, vacuum off the bees and place in a covered container.
2. Once the bulk of bees are vacuumed, take the comb and frames somewhere protected and band the comb into the frames. I did this in the open, right next to other hives, and the robbing was ridiculous.
3. Then, put the frames into the box and immediately dump the vacuumed bees into the box. then, close it up and put an entrance reducer in place (or temporarily close the entrance altogether, which might be an even better idea).