I had an issue some time ago where one of my Armorers “disappeared” because when moving the cursor up from the slots below to the Thrall spot I didn’t quite go far enough and landed on the “non-existent row” in between the Thrall spot and the inventory spots below (hope I explained that well enough).
Anyway, once we put another Armorer in the bench and put it in the Thrall spot, the missing Armorer re-appeared in the inventory spots at the bottom. Try taming a T1 or T2 priest to put into your Thrall spot and it may knock your other priest loose again.