Poor quality merchandise

I received an expensive UZZI shirt for Christmas as a gift. The first time it was washed it shrank at least 2 sizes. It was washed exactly in line with the label instructions. Truworths has refused to do anything about it because I cannot provide the original proof of purchase. All I know was that it was purchased from the Whale Coast Mall Herm**** branch. How do I provide proof of purchase for something given to me as a gift? I have written to Customer Services and they told me that is the policy so tough luck. Truworths is happy to supply defective product and not accept responsibility for any defect..