Where are the rest of the Cambodian Statues?

Pierre Ciric, Tess Davis, Max Howlett, Matthew Rendall, and Sun Samnang, 'Opinion: It's Time to Stop Profiting from the Killing Fields' Art-net news Saturday, November 1, 2014 discuss recent returns of statues looted in Cambodia's civil war.

It is not surprising these statues have now been returned to Cambodia, but that more have not followed. It is morally abhorrent that some museums, dealers, and collectors continue to profit from the killing fields. It is also illegal. Cambodian ownership laws have always been clear and unambiguous, and likewise, they have always been enforced to the best of the country's ability. As the capitulation in the Sotheby's case reveals, there are now no moral or legal grounds to deny the Kingdom of Cambodia and its people the rightful restitution of their national patrimony.

What is notable is that the statues that have gone back only result from outsiders spotting a dodgy artefact leading to a challenge. Not a single one of these returns has resulted from a collector coming forward voluntarily with an item they realise has been illicitly and immorally (not to say illegally) obtained.
That tells you something about collectors and museums.