Duplicate Loot in CT

I'll start off by saying that I know this is not a bug. At least not by any definition of "bug" I've ever heard. It's just a dumb thing that can happen. But several GMs have insisted that they can't help me and that I should post here, so here you go. I'm sorry if this doesn't belong here.

Time: Monday, February 3rd, 2014, 2pm-ish CST
Frequency: Once
World name: Gilgamesh
Character name: Kai Vastra
NPC name: N/A
Monster name: N/A
Class/Level: 50 Dragoon
Party or solo: Party
In-game time: Unsure
Area and coordinates: Labyrinth of the Ancients
Steps:
1. Kill a boss.
2. Open the chest.
3. Click greed on an item you already own when you meant to click pass.
4. Stare in disbelief when the useless duplicate item is awarded to you and your weekly roll is wasted.

Pretty sure my system info isn't needed for this. On the off chance I'm wrong, just say the word.

Was the item in your inventory/armoury chest, or was it on retainer?