As someone who worked on the tills in a supermarket in that period, I was expected to make sure the signature matched with the signature on the card.
Jen, I'm sure you were a youngster at the time, and a very diligent one, but the police told me: "A lot of these shops are staffed by teenagers who don't give a ****"
In my case, the thieves bought a packet of fags and asked for £40 , or remainder thereof, cashback. They did that three times in one street. It was early days of CCTV but the cops matched a transaction record to an image. "Did you recognise the thief? " I asked.
"Well, it was a guy with a hoody and a baseball cap" they shrugged.
The bank cancelled the transactions and the ultimate losers, unfortunately, were the small retailers.