If it were me, I'd pay the $20 to the seller on e-bay, finish the quilt and post a photo on my sewing room door reminding me to double check EVERYthing before I begin sewing!!!!! Then I'd chalk it up to a learning experience and move on...
Whatever you choose to do, making your sil a quilt is a lovely idea.
Sally

Also you must remember that you know what the quilt kit was supposed to look like. If you substitute fabric, or use different fabric for the setting part, you are making it your own design!