The sale of goods act states that items sold have to be of a reasonable quality. Normally, this would mean you would need a reciept. If you have a bank statement with the item you purchashed on it, they should accept this. They might state it was damaged due to misuse, in which case, they wouldn't need to.
However as an goodwill act I would have thought they would give you an exchange at the least (providing you have the statement with the purchase on).
The sale of goods act, 1979 is what you need to learn about.
Hope this helps