Lost Iridescent Flightstone

Upon investigating in the Customer Support FAQ I found a line of text that I hadn't seen anywhere else about this.

"A Timewarped quest item will drop from the last boss of your first Timewalking dungeon for characters level 30 and above. If you are playing a character that you used a Character Boost on, they must be logged into the game for one hour before becoming eligible."

So all of the characters I had run it on previously were under level 30. I then ran one on my Level 83 Paladin and received the item at the end of my first dungeon. I'm not sure why this item is restricted to lvl 30 and above but this seems to be the answer. Hope this helps others!

Quest items for the different Timewalking events:

Classic: [item=225348]
Outland: [item=129747]
Northrend: [item=129928]
Cataclysm: [item=133378]
Mists of Pandaria: [item=143776]
Draenor: [item=167922]
Legion: [item=187611]
BfA: [item=238791]
Shadowlands: [item=253517]
Dragonflight: [item=262918]