I'm not saying it wasn't {Company Name} cuz I don't know, but if you have made any purchases with that card in the last few months, it could be from any of them.
A few years back I was using network solution's hosted shopping cart on one of my sites when millions of cc numbers and accompanying id info was stolen from them. Network solutions didn't bother to notify me for a few months (they said because they were "internally investigating") so by the time I found out and scrambled to notify my customers, nearly 3 months had passed. From the info I was able to gather, the offenders sold the cc info - so some people were hit with fraudulent charges right away, others weren't hit until much later. I don't know how often it happens this way, I just know that it does happen.
Sorry this happened to you and I hope you get it straightened out without too much trouble.