There were two critical hive skirmish missions for Dantia F-5, one said there were 100 losses left, the other about 50.
I took one, killed the queen, and the mission completed with the hive leaving.
There were two frigates fighting the queen, not sure if that's unusual.
I didn't see any other queens, but wasn't really looking for one.

Then the other critical mission for F-5 was still available, I accepted it, but the sector was already clear: no hive bots left, only my old npc groupies leaving. The score bar (Serco: ###/Queen) didn't show up either.
I ended up aborting the mission. After that it was still available on the mission board.

Were both missions posted at the same station? Do you know around what time you completed the first one?

Yups, they were both posted at the same station, 99% certain it was Dantia K-6.

I completed the first mission a couple of minutes before making the post, it went something like this:
Take mission 1 - jump to F-5 - drop queen shields - have NPC groupies kill queen, completing mission - return to station - take mission 2 - jump to F-5 - notice no hive bots around - notice no score bar - return to station - abort mission - make post
with not much pause between actions, so I probably completed the first mission somewhere between 5:30 - 5:45 in this boards timezone