I'll understand that the fabric store is faultless, but nevertheless you do need to go through the store, to get to the manufacturer.
Go to the store and talk to them, they seem to be nice and will understand. They want you to be happy to. Don't worry about the fabric being cut already.
Give it a try, to much money and happiness are at stake here.
The store will pretty much have to send the fabric back, that's for sure, but I'm also sure, that you will get what you needed.
See all of this, doesn't need to be done in with bad feelings. May be from now on Northcott will better take care of their cuttings.
Go to the store, I know together it will get solved and everybody will feel better.
I do would like to see the quilt!