Sleeveless Belted Denim Dress

I recently purchased this denim dress in size XS and I really like it overall. However, it was supposed to come with a belt, and unfortunately, the belt was missing at checkout. The cashier kindly tried to locate it but wasn’t able to find one. I asked if there might be a small discount since the item was incomplete, especially because without the belt it doesn’t fit me properly. I was a bit disappointed with the response, as I was told that no adjustment could be made and the only option was not to sell the item to me. I still like the dress, but I hope the customer service experience can be improved in situations like this