Did anyone ever get any resolution here? There’s another post here Epic Purple Shirt is gone from my inventory - #33 by Kiekö-laughing-skull with a similar issue and it looks like the issue truly is widespread with no recourse or acknowledgement from Blizzard.
A simple fix here would be to make these physical items account-wide unlocks from Landro if you have unlocked the appearance. (This would give people who received some as Twitch promotions the physical item instead of just the appearance which I think is fine).