How likely does this indicate criminal activity?

I got a confirmation email this afternoon from Priceline for a rental car reservation made for several weeks in the future. Problem: I never made such a reservation. Calling Priceline (using a phone number I got from their web site, not the email) indicated that somebody did make the reservation indicated in the email, using my name and email address but not my credit card or phone number. This was surely malicious, but how likely is it an attempt at fraud?

P.S. Priceline washed their hands of the matter, saying that there was nothing that the reservation could not be changed or cancelled and that was that, no matter what the circumstances.