That damage did not happen within in a week. It takes a lot longer than that (months or years) for the leaking material to completely dry out, corrode metal, and crystallize to form that powdery alkaline salt. If it has only been a week or two, it would still be wet and oily.
However, if the seller won't make it right, then you can try to contact Duracell, since the battery has leaked before its expiration date (2024). They will likely ask for photos and the replacement cost of the board.