It was inconsiderate and poor customers service of them to send the supplies knowing that the pattern is on backorder. You obviously wouldn't be ordering those particular items if the pattern is not available.
This site says that the pattern is unavailable and your entire order will be shipped all together when it does become available.
I was going to suggest that you file a complaint with the Better Business Bureau. If you ordered form Cross Stitch Unlimited in New Jersey, they have gone out of business. Maybe because of poor customer service.
Did you order using a credit card? If so, I would contact my credit card company and see if they can get an adjustment for you. Same thing if you used PayPal.
Sorry that happened to you. Welcome to our chat group.