I've collected my debit card from the customer service desks at both Tesco and Morrisons on several occasions ;-)
When 'cashback' was first introduced in shops, many of them required customers to sign the receipt to show that they'd received it. I asked for £50 cashback in Morrisons and was presented with the receipt to sign. It wasn't until I got home that I realised that I'd signed before receiving the cash and that I'd never actually got it! (Fortunately Morrisons were very good at sorting my problem out).
I ordered a coffee in a Wetherspoon's pub in Rushden and, once again, asked for cashback. (£30, in this case). The barman had some problems with the coffee machine, meaning that it took quite a long time for me to get my coffee. By the time I got my coffee, I'd completely forgotten about the cash and I didn't notice the error until I was back at my hotel later that day. (Luckily for me, my transaction at the bar had been been carried out immediately below a CCTV camera and the manager was able to check my story very quickly when I phoned the pub).