I don't think it's that hard to buy discretion if you're willing to pay a hefty fee. Besides how could anyone prove that you actually own the painting? I hire you, I fly you half the way around the world to a remote place where you're to examine the painting for a couple of weeks, you're paid and bye-bye.

I'm not saying that I know for a fact that this is how it's happening, but it doesn't seem far-fetched. What I do know is that a lot of what's happening in the art world is shrouded by a veil of secrecy.