You are not alone. Last month I had a charge on my credit card that was not mine. It is a credit card that I do not use often, only for medical bills mostly so I know the theft occurred at the doctor's office or the billing center. None one else had access to the number. I promptly canceled the card and got a new number. I would recommend that you check your credit card activity daily.
I did that once, cancelled my credit card before a charge was able to be put on it. That was a case of someone offering me something I thought was legit and turned out to be a scam. In a way, I'm glad I'm not alone in this and in another way I'm sorry this kind of thing happens. I will be diligent from now on. I do keep running tabs on my bank account and when there's a charge I don't recognize, I call the bank. It has always turned out to be myself who paid for something and forgot to write it down in the register.