Likely from a skimmer, just like you thought. In the Fall of last year, I used a credit card at a take-out restaurant in my area and about 2 weeks later, someone tried to use a duplicate of my card in a neighboring city--only the card they copied had a chip so it wasn't accepted at the Target where they tried to use it. I tried to use the card and it was declined, so I called my cc company and they asked if I had tried to make a purchase at Target for a few hundred dollars, and no, I hadn't. I called the police and had a policeman come out, explained to him that the only place I had used the card in a few months was at this take-out restaurant and I was pretty convinced that someone there used a skimmer or otherwise copied my card. I wanted someone to investigate this restaurant.
He said that I could file a report if I wanted but the detectives in my area were pretty busy dealing with major crimes like murder, rapes, and major robberies, and since I actually wasn't a victim since they were unable to use the card, my case would take weeks for anyone to get around to looking into...plus he tried to make the case that there are multiple other ways that hackers can get a hold of someone's card number to duplicate a credit card and use it across the country...at which time I pointed out that the attempted use was in a city about 12 miles away. He said, "Yeah, but still, you aren't out any money and your credit card company would take care of it even if you were." He seemed very disinterested and made it clear that it was not a priority, so I just dropped it.