Merchant is contesting a fraudulent charge – what are the odds they are successful?

About two months ago I had a slew of fraudulent charges on my credit card. I noticed them quickly and disputed them as fraudulent with my card, and all were refunded within days.

One of the merchants now is disputing the fraudulent charge. They've provided lots of documentation that they claim proves that I made the charge (including that the credit card information matched the billing and shipping address – this information was used as well although my address is not a perfect match and is missing the apartment number). I'm still not sure why the fraudulent charge was made in this way with my actual information, but it was.

The merchant also provided the IP address from which the charge was made – which I think may be my saving grace because the location does not match my location or anywhere I've ever been.

My credit card company just asked me to sign a document stating that I did not make the transaction. But I'm nervous that the company will be successful in "proving" in some way that I made the charge. It was a substantial amount of money. Has anyone had this happen and do I have anything to be worried about?