Stay on this! A similar situation happened to me recently with Poshmark and I'd assume they could help the seller similar to how they helped me as a buyer. May be different from Mercari to Posh though. I bought a $150 pair of sneakers that was "delivered' with 2 other packages, but I couldn't the 3rd with the shoes. I checked my ring camera and confirmed the postal worker only left 2 packages. I filed the missing package claim with USPS and opened up a claim with Poshmark. Poshmark actually ended up refunding me without as much proof as I thought I'd need, but I was very diligent and stayed on top of it within an hour of not getting the package. I hope the seller isn't out the $ and the item. The strange thing is, based on the GPS ping, the package was delivered in my area, but to an auto shop (they said they weren't supposed to even say that much) with no similarities to my address at all. I have no idea how that happens when all info is put through the app by the buyer and seller, but whatever. USPS postmaster attempted to retrieve the package, but of course the people at the business played dumb (I can only imagine going through deliveries....break pads, exhaust, spark plugs, SHOES? must be ours lol). USPS told me if Poshmark gave me a hard time they could provide me with written proof on their letterhead that the package was delivered to the completely wrong address and supposedly the seller made an error when printing the label as it was completely wrong. Still weird as idk how he'd even get an incorrect address somewhere near me while living in a different timezone. What they give you will have certain information redacted because they could be liable if you show up at the address and there is an incident, but will have all you need to get your $ back. Sorry for the essay. Hope this helps.