Buyer claims to have received a random top - anyone have any luck querying with courier?

Sold a green PU leather jacket on vinted, the buyer picked it up a few hours ago and immediately raised an issue saying they got a random top.

At first I thought it was a scam of some kind but they have only good reviews as a buyer with a large history, so I'm leaning towards it being InPost that's at fault?? Does anyone have experience getting in contact with them to resolve? I don't really want to be out of pocket either but I have no other proof of posting the correct item, I thought my inpost receipt would suffice!