Fulfilled By Amazon would provide no protection here.
When you send a replenishment shipment to Amazon for a FBA item, they don't open and verify you sent the correct product. You only find out about mistakes after the items have been sold.
For some common FBA items (presumably like an iPhone), you can co-mingle your inventory. This means you send in an identical item (with UPC, etc), and your inventory can be used to fulfill another seller's order (if that warehouse happens to be closer to the customer). They do the same for you.
This means buyers get their order faster, but it also means the item going out the door may not have been yours (opening the door for this clay scam to spread to impact many many sellers).
I would be very surprised if Amazon actually mixed up merchandise from several sellers to the point that they don't know where the items originated.
It's one thing to ship from the closest warehouse and credit the sale to whichever seller offered the price chosen by the customer. It's a totally different thing to not know where the item came from at all.
That's not what I implied. They track inventory internally, but your item may ship from your local FBA warehouse to someone else's customer.
This does leave a door open for many items to ship before any error was realized... (sometimes within a few days, but usually up to a few weeks after it happened).
When you send a replenishment shipment to Amazon for a FBA item, they don't open and verify you sent the correct product. You only find out about mistakes after the items have been sold.
For some common FBA items (presumably like an iPhone), you can co-mingle your inventory. This means you send in an identical item (with UPC, etc), and your inventory can be used to fulfill another seller's order (if that warehouse happens to be closer to the customer). They do the same for you.
This means buyers get their order faster, but it also means the item going out the door may not have been yours (opening the door for this clay scam to spread to impact many many sellers).