Dischem service is the worst I've ever had

A month ago I bought an electric hot water bottle. When it stopped working I returned it to the same store together with the relevant till slip. But I was told I could not return it because I don't have the box it came in. This is totally unreasonable, if I had to keep the box from every item I buy, I would have to buy another house to house them all. Besides, to my knowledge, it is ******** to refuse to exchange or repair a faulty item. It has a year's guarantee. Also there is dishonesty here because nowhere on the package nor in the store are you told to keep the box. Last purchase EVER from Dischem.