Swarm Today, Gone Tomorrow!

I couldn't believe it!  Today, Dawn & I drove to the farm to feed the bees and see how the six hives were doing.  When I open the hive containing the swarm from Thursday night, it was empty!  They were gone!  The swarm swarmed!  Dawn & I are totally bummed!  The Friday swarm was still in their hive, and I hope they remain there!