So here's the situation.
I have several WO active and only one complete - I teleport to my Garrison and check the completed WO - it's the Hearthstone tournament. It requires 3 followers.

I complete it, claim the reward, and then I decide to check which WO should I do next with those 3 followers.

However... there are only 2 followers showing as free for work. All other followers are on the missions for quite some time now.

How is this possible? I can't recall which followers I used for the tournament, but does it really matter? Apparently when I started the hearthstone work order, I somehow managed to use one of the already at-work followers, it's either that or one of my followers magically disappearing from the garrison.

Anyone had this happen?