If you pay everything by card then you don't need a reciept to return it. All you need is proof of purchase; the section of your bank statement showing the payment qualifies as proof of purchase. They can track down the rest from there
I was really impressed when I had an issue with some gift cards I bought from Morrisons. I should have had them activated, but just paid for them at the self service till and when I came to use them, they didn't work (it was getting Now TV at a discount, not actually giving them as gifts luckily).
I'd lost my receipt but could show them the credit card transaction on my phone in online banking. From that, they went into the till and got a list of everything I'd paid for in that transaction, saw that I'd paid for the gift cards and then activated them for me.
I would use email receipts more, except that I don't trust the shops not to use this to bombard me with marketing crap, even though it's illegal to sign people up without permission, they all seem to do it.
I also can't be arsed to be constantly spelling out my email address so that they enter it correctly, because my first name has two spellings and while to me, my last name is easy to spell and pronounce, being the same as a fairly well known place, even when I say it and spell it, people always take it on themselves to spell it in a variety of different ways and pronounce it differently when they say it back to me
, so the chances of someone taking my email address down correctly is quite slim.
Although I do like the screen in Uniqlo, where you type in your own email address to get a receipt.