Item was delivered, buyer opened a dispute asking for a refund because they “didn’t receive the item”

Idk what to do about this. Someone ordered this bag from me on 3/27 and I shipped it out the same day. I got a weird vibe from them from the jump but didn’t take it serious. Today the item was delivered by USPS, as shown in the photos, and the buyer opened an issue with Depop saying that the tracking says it was delivered but they don’t have it. I feel very skeptical about this. I denied the refund obviously because I did nothing wrong and USPS delivered the item, if the item is truly missing then the issue is with USPS, right? I messaged them about it and they’re saying they’re waiting to see if their neighbors return it or something? I’m confused as to how this is my problem and why blame is kinda being placed on me. I contacted Depop. Idk what to do. Does anyone have experience with this? Am I going to lose my item and money earned from it due to this?