I tend to prefer to resolve issues for both sides rather than embarrass people. So rather than playing "gotcha" ... when evidence emerged that a few heads which had passed through auctions seemed identical to ones that had come out of recent excavations in North Africa, I dropped a few dealers an email to try to sort out the issues. All were helpful except one.
Some colleagues, archaeologists I hold in the highest esteem, told me that Christie's had ignored their worries about one such head.
My experience of Christie's is that that's par for the course, but just in case ... I knew they couldn't give me the buyer's details, so I asked the head of department, Ms Georgina Aitken, to pass mine on to the buyer as I had some information about the history of the piece. Ms Aitken said she would not do so unless I told her what the information was. I briefly explained that there was evidence to suggest that the head might have been looted and that the provenance was faked, and that Christie's were aware of this and did nothing. There are more chances of pigs flying than of this information being passed on to the buyer ...
This is what pisses me off about the art market. Someone who doesn't know what they're doing can't resolve what should have been a simple issue - gain some goodwill by trying to see if this head is the same as the excavated one, and return it to its country of origin if it was (or have no more issues with it's history if it wasn't).
Instead ... A collector is going to be surprised that he bought a piece which might be hot.