If you still have the receipt or a charge on a card I can't see how they won't give you a replacement part or a refund.
I would definitely be contacting NAPA headquarters(be direct and polite).
NAPAonline.com
Contact link @ NAPA Online
There is a contact form, a listed email address you can use and this :
Phone
For customer service, including product information and order status, contact us at:
1-800-LET-NAPA (1-800-538-6272)
Hours: 8 a.m. to 5 p.m.
Eastern Time
Monday – Friday
... and if that doesn't work... go old school :
Napa Auto Parts Corporate Office Headquarters
National Automotive Parts Association, Inc. (NAPA)
2999 Circle 75 Pkwy SE,
Atlanta, GA 30339 USA
Corporate Phone Number: 1-770-956-2200
Fax Number: 1-770-956-2212
Customer Service Number: 1-800-538-6272
Napa Online: 1-877-805-6272
-W