Seller refusing to confirm return

Unfortunately, due to an emergency, I was unable to collect an item in time so it was returned to the seller. I apologised profusely, and they said it was fine.

Fast forward, the item has been returned (over a week ago according to both the app and the courier) but the seller is refusing to confirm they have it. They are now pretending to speak bad English, sending weird messages that make no sense, when it's perfectly plain from their reviews of buyers that their English is word perfect.

Vinted themselves have said I have to wait 5 weeks for a refund if the seller doesn't/won't confirm the item has been returned - is this so? If it is, then this is another reason to add to the list of many to not buy from Vinted...