Guild Wars 2

Do previous reward items such as the Fused Gauntlets unlock in the wardrobe if you’ve won them, but discarded the item over time before the update?

I’m just curious since my main has unlocked tier 3 cultural armor and many other cosmetics, but never managed to save them before the update.

No. You have to have the item at time of patch day. You can open a ticket, but it is highly unlikely that anything will come of it.