I looked into Hive B a few days ago and found no brood and no Queen. The colony is quite small so she probably wasn't hiding.
Is there a virgin Queen waiting to take over? That would be reasonable following the supersedure which I saw in progress at the start of the month. I will have to look again to see whether brood returns. What happens if the colony is unable to create a new Queen? I'm unsure.
The colony in Hive B is small and hardly thriving compared to other colonies I'm working with. It appears to have been a cast swarm and this fact - followed by the hungry gap - may explain a lot.