Cannot proceed with Arbiter quest

I killed both bosses for quest: Geonor and Doriani. Unfortunately, I faced an issue with the first one. After kill, i clicked on the teleport item for an accident, after teleporting down I came back, used a checkpoint to come to Arena, but the boss didn't have loot already. I did not receive a quest item to proceed on Arbiter. The second one fragment was received.
Can this problem be resolved somehow? Im just stuck on progressing Atlas.