I understand that fulfilled by Amazon is not the same as sold by Amazon, its on me for not being clear enough. I am not inquiring as to FBA and would not even know how you could research it because you would need to know the terms of the agreement between Amazon and the seller as to possession of the goods which are being FBA.
My only question is as to items which are "Ships from and sold by Amazon.com" as to whether there is a concern of Chometz She'Avar Alav HaPesach.