Where There Is Smoke - MSQ Halting Bug

Date & Time: 18/12/2019
Frequency: Once, unable to advance
World name: Phoenix
Quest name: Where There Is Smoke
Character name: Tsub Amariyo
NPC name: Hihibaru
Monster name: Corpse Brigade Footsoldier
Class/Level: Archer 28 and a Machinist 80
Party or solo: Party, 2 members
Area and coordinates: Eastern Thanalan ( 27.7 , 16.3 )

Steps:
1. Advance quest until the point you place the smoldering coal to lure the footsoldier
2. Have a high level party member one shot the enemy before aggroing it
3. The enemy does not drop the key item required to finish the quest, however the quest is marked as complete, therefore can not be turned in.

The quest can not be finished, the enemy can not be respawned and the quest cannot be abandoned. MSQ is halted and no further progress can be made.

This is how to reproduce, to the best of my knowledge. I did not realise I was missing the key item until I attempted to turn in the quest, and after checking wiki for the quest, found it was missing.

Connection Specs
- Type of internet connection/provider: British Telecom, Fibre, 300/100
- Modem maker/model number: BT Home Hub 3
- Connected through NordVPN

Screenshot of the quest marked as complete, with the key item missing from my inventory:
https://i.imgur.com/J1DbydY.png

Try doing an item reclaim from a Calamity Salvager and see if that works!