THIS X10000! Happened to a colleague of mine not too long ago. She developed a product, and sold on Amazon as well as her own storefront. As soon as she started seeing solid volume on Amazon, her product became an "Amazon preferred product" or something like that. However, within 2 weeks of getting that distinction, her sales dropped to 0 on Amazon. Why? Amazon started selling a nearly identical product - Amazon used the sales data to understand her product was popular, and went right to her supplier and cut her out of the equation.
Amazon does this constantly.