Good luck. Their return service is terrible. You will have to ship it back at your own expense if they do not accept the issue. I am sure they will accept yours though, at least I hope they do.
I tried to send back a brake pad and rotor kit for my wife's car which didn't fit and ultimately kept the kit because it was going to be $200+ (over half the price of the kit itself) just to ship it back to the warehouse where it came from. The reason RockAuto wouldn't accept it on their dime was because I received "what I intended to order" (total BS).
I thought that a nice upgrade from the solid rear rotor to a vented rear rotor would be a great idea. However the description of what the kit included was not just a description, but a warning/requirement that meant if my car did not come with a vented rear rotor this kit would not fit. Keep in mind that it was in the provided list of parts made for the year, make, model, and trim level of her car. There was no warning anywhere throughout the whole purchase process that would have told me it would not fit on a car with a solid rear rotor. I even went to the manufacturer site and they didn't have it listed anywhere. I have a love hate relationship with them because of this.
Lesson learned was make sure 10000% what you order is what you actually want to get, including verifying fit on something you haven't installed yet.