Second try at posting this:
I was buying an artifact from the artifact shop at the same time the controlling flag for that shop was being captured out from under me, and I was on the brink of death.
I sold a Hauberk of Life to make room, and then attempted to buy a Magebane. The money was deducted but I did not get the item.
My theory, though I can't confirm it, is that I paid the gold in the exact instant of death, and then I wasn't allowed to actually get the item because I was dead.
