I didn't sell this party any parts. Now, what made the party think they had bought a part from a certain party. Their credit card was charged for the purchase. They received the part. End of story unless there's a problem with the part.
Many businesses use a credit card service provider.
It's not unusual for monthly statements to show purchases credited to someone other than the seller. Many businesses drop ship, so it's not unusual for a part to arrive from a third party. The purchaser had used a major search engine to find the site, found the site in a major magazine ad or found a legitimate site trapped in someone's frame and went directly there to make the purchase. Skater Nancy Kerrigan was successful in her lawsuit against a porn site. While no pictures of Nancy were displayed on the site, the sites meta-tags used her name to have the site displayed in results of a search for Nancy Kerrigan.