The so-called good faith purchaser is NOT a victim. Period.
There is something called 'due diligence' which any self-respecting purchaser of art, especially of objects that are expensive, as in the thousands, tens of thousands, hundreds of thousands of dollars or euros and up, must engage in prior to the acquisition. In other words, the same principles that apply to the acquisition of a car or a house apply to the acquisition of art. That's not very complicated to understand, except for the fact that, until recently, when all the hullaballoo about looted art entered into our conscious frame of mind since the late 1990s, no one seemed to truly understand that those works of art being considered for acquisition might have been involved in some kind of man-made catastrophe like genocide, mass slaughter, civil strife, or other human horrors perpetrated on other human beings, resulting in outright thefts of victims' property.
The inability and/or unwillingness to do one's due diligence is a continuing plague on the global art market writ large, including museums, galleries, art fairs, and individual collectors, brokers, and dealers.