The Case of the Disappearing Honey!

We've had quite the year keeping honeybees and already had to combine the two hives on August 25th.  I fed them immediately after introducing the two colonies and checked for new brood.  Everything looked fine by the end of September and I fed them right up to when the fall nectar flow began.  By the beginning of October, the hive was a good weight and I left them alone.  This past weekend I decided to heft the hive and was thinking of feeding them since the weather was warm Veteran's Day weekend.  Come to find out, the hive was light as a feather!!!  Jon and I suited up and went into the hive to find maybe one frame 1/3 full of nectar, a few cells of pollen, and no brood.  The queen was still alive and moving around.  What's interesting about this scenario is that this is the exact thing that happened to one of the hives before we combined them in August...they were completely robbed of all their honey stores!

I think this is a bit odd considering the hive was a good winter weight less than 2 months ago and they were busy during the nectar flow.  I think the hive had been robbed out by another hive...perhaps one in the woods or from another beekeeper's hives 1 mile away?  This May during swarm season, Jon and I were gone for 2 weeks and we suspected that one hive swarmed so perhaps they found an old tree and got established?  The yellow jackets have also been up by the hive a lot the past few weeks and I squish them when I can, but in hindsight, I should have reduced the hive entrance to discourage robbing.  Whatever the reason, we're not happy because there really is no way to save this hive.  In a month or so I'll gather up the empty boxes and store them for next year.