After the NA server crash yesterday, I have had a thick black lamellar vest in my in-game inventory (but not on the website). I didn't own a black lamellar vest beforehand, let alone an heirloomed one.
All my other items are exactly the same as they were before.
After a bit of testing, closing and restarting warband doesn't get rid of it.
I can buy a black lamellar vest and it appears both in game and in my inventory on the website, alongside the thick black lamellar in game.
Selling the regular black lamellar vest works as it should, the vest disappears and I get money, but I still have the thick black lamellar in vest in my in-game inventory.