Item disappears after cancelled trade

Was checking the value of an item at NPC vendor, after cancelling the trade the item disappeared. The log showed that the trade was definitely cancelled and not a mistake on my part.

The item had gems in it, perhaps this was the reason?

Edit: It seems I received the payment for the item as if the trade went through normally, so I guess the item did not actually vanish, it was traded fairly. Still, I'm almost certain I clicked cancel.