Vinted complaint: Item not damaged but box was dented

I sold an item on Vinted for £50, Harry Potter Hogwarts Express Lego, It was brand new and in perfect condition before I sent it and it was damaged in transit, well the box was dented in one corner. Vinted cancelled the order and refunded the buyer, the buyer has not sent the item back. The Lego is still sealed in the bags with the instructions in brand new condition, the box was still sealed and Vinted are saying that there’s nothing they can do and it was my fault for the item being damaged. But the item that the buyer brought is in brand new condition and not damaged, it is superficial damage to the box.
I am disgusted with how the Vinted team have just copied and pasted the same message to me each time saying that there’s nothing they can do.
I have asked for proof of the damaged Lego as this is what the buyer has paid for.
I feel that this is unfair as £50 is a lot of money and I haven’t had my item returned to me so the buyer has received a £90 Lego in perfect brand new condition for free.
Vinted are a huge platform and the customer service has been abysmal.
I am so upset that this has happen. I have deleted my Vinted account and I am not selling on there ever again.