In the future, if paying at the pump, check for two things. By law, there’s supposed to be an anti-tamper seal on the panel for the credit card reader, if it’s missing or otherwise not sealed, report it to the station.
Also, give a gentle shake on the card reader itself. Some have become very hard to detect visually but they’ve yet to discover a good method to get them to adhere to the real one. A slight shake and they typically fall off or pull out. I’ve found two over the last 5 years at the closest station to my house, which is located right off the interstate, by using this method.