Hi!
On my way to the Dry River, I successfully found the clues of the missing merchant and then got attacked per quest trigger. The quest is not foolproof however, as leaving the zone and reentering it will not spawn the scarab again.
The first trail of the body can be interacted with (shown as grey ?), but the second is nowhere to be found, and interacting with the merchant (shown as golden ?) will trigger no dialog box. My quest progress is stuck on having found the merchant and then dealing with the scarab.
Please investigate!
Update: The quest can be completed by talking to Ritolo in the Upper District. The Scarab won’t spawn at all as described, but talking resolves the issue.