Kiernook is gone?

Checked. Kiernook and Yulina, the two cooks, could appear underneath the banquet hall floor in some runs. That is why the minimap showed them while they were nowhere to be seen; the second "invisible enemy" you saw was Yulina. This was fixed with the patrol fixes from your earlier report, and on the updated server both cooks walk the hall together in every run. Live after the next server update.