I was alone without a party and no auto loot. I was attacking it alone until like 5% hp when a party came and last hit it, then only the daily quest appeared as it was cleared for them and the boss went pooff.
Εξαφανίστηκε τελείως όταν triggare το daily quest, οπότε υποψιάζομαι ότι κάποιο bug από το daily να είναι.. Ελπίζω να βοήθησα..
Maybe with auto loot i could still get drops? There was no boss or chest to click at...