The other day I was using the self-checkout and noticed that whoever had been in before me had been issued a £5 off voucher. They were obviously long gone and, as they hadn't taken the voucher, were probably unaware they'd even earned one.
I thought about it while I scanned my shopping, but assumed if I handed it in then the staff would probably either throw it away or use it themselves. So I scanned it and got £5 off my shopping.
Feeling a bit guilty, but does it matter?