knight boss disappeared in the hunt site of power

I was fighting the bosses of the site and I ran up the ramp that leads out whilst the knight was behind me and the knight disappeared when I jumped back down at first I thought he was stuck but after killing the bishop the alter opened meaning both were dead I'm pretty sure he fell thought the map snice I didn't hear him die i haven't seen anyone else talk about this so it might be a rare bug or a one time thing