Well, you can't really do much if you don't have the receipt. Learn a lesson about keeping receipts for expensive purchases? Look harder? Try very carefully not to break it? Sell it on eBay if you do break it? Go to the store you purchased it and beg?
On more serious suggestions: if it was purchased with a credit / debit card, or if a loyalty card was used, kind and generous stores might well be able to check the sales records as a proof of purchase. My brother managed to return an Xbox without a receipt on the basis of the loyalty card's record. Though he sent my mum as he thought they'd be more receptive to a woman.
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