Cardiologist Buys Antiquities in London - Seized in US

The Asia Week seizure from Christies is in the news again ((Rashmi Menon. 'Christie's auctions cardiologist Dr. Lahiri's artworks for $2,376,500' Economic Times 18th May 2016). Concerning these pieces, auction house Christie's said,

"Christie's devotes considerable resources to investigating the provenance of all objects we offer for sale. Under no circumstance would Christie's knowingly offer a work of art where there are valid concerns over provenance. "Government officials have informed us that the evidence they uncovered determining that Lots 61 and 62 were problematic was not publicly available and, therefore, could not have been accessed by Christie's for vetting purposes.

So, this is "Negative Vetting" (not on a list of items known to be stolen), rather than "Positive vetting" (we have verified from what legal sources this item comes). The trouble with Christie's methods is that (unless a dealer was careless and did not destroy his business correspondence and it falls into the hands of the authorities by accident) looted freshly-surfaced (from "underground") material never figures on a "these items are stolen" list. Even my cat knows that. Dr Lahiris should have known that - does he get the medical supplies he uses from dealers who supply them without proper certification of origin but can only show they are "not on a list of known dodgy stuff - so must be OK" ? I hope not.