I've wondered if Amazon co-locates its own stock with that of Fulfillment By Amazon stock which would mean you could end up with anything as long as it looks similar and has the same SKU.
This is the reason why I quit buying anything from Amazon anymore if I can help it. They're not interested in fixing it.
What I can't understand is this: even if they comingle, they must know which seller owns which item. If they didn't, how would they pay the right seller once a particular item is sold? And yet, there seems to be no accountability at all.
They don't need to know which product belongs to which seller, they only need to know how many.
If someone clicks your listing and buys a product, they ship it from the commingled inventory and then pay you your share of the sale and deduct one from your inventory tally.
Then, if the item they sent ends up being counterfeit, whether from your own stock, from another seller, or even from Amazon's own stock, they will take it out on your seller account for selling counterfeits.
Not necessarily, some items have only one listing for all sellers and you click the buy button that has the prime logo. Who are you buying from in this case as far as Amazon is concerned for their inventory accounting?
It already is. As you can see by everyone here talking about it, it's beginning to cost them sales. I imagine there will be a big campaign by Amazon in some years from now about them "trying" to fix this problem.
As a vendor you have to pay Amazon extra to avoid comingling - basically you have to get a new item number assigned and product you're selling all has to be tracked by that number.