Pathetic excuse and no options

Half of the order was missing upon arrival. The item purchased was a tankini set (IE top and bottom), bottom was missing. Complained immediately to only receive a response 2 days afterwards and after sending a chaser email. The response promised an investigation and while the reply to this came quickly, it was advised that the warehouse cannot locate the missing item and that I should return what was sent and get a refund. I explained to the support team that I would prefer to keep the top rather than return it for refund but would like them to send me the bottoms that should have come with the top. That was 6 days ago and no one has bothered to reply back. Absolutely ludicrous that an error or possibly even theft in the warehouse results in only half an order being sent and then, as the customer, I don't have any option but to return the other half of the item for a refund. Surely there are other bottoms available to send??? Ludicrous. This is the first and last time I purchase anything from Spree.