How can an Apple Card purchase be approved but payment not go through?

This afternoon, I used Apple Pay on my iPhone 16 Pro (iOS 18.4) to make a purchase on my Apple Card at a retail store. The order was for an item to be shipped to my home, and was placed using my membership in the company's rewards program, so they had all my contact info.

The transaction was approved by Goldman Sachs/Mastercard and the merchant system emailed a receipt to me. Oddly, the transaction didn't show up in the Latest Transactions list for the card in Apple Wallet.

Then, 53 minutes later, the merchant sent me an email saying that the payment for my order did not go through. The email said I would have to call them within 72 hours with a "new form of payment" -- otherwise the order would be cancelled.

I've never experienced this kind of thing happening before, and I've been using credit cards for 30+ years. How is it possible that the bank (obviously) approved the purchase but then failed to properly process the transaction on behalf of the merchant? By the way, my current balance is about 2% of my Apple Card credit limit, and my previous month's Apple Card balance was already paid in full.

If this had been a purchase of an actual item they had in stock at the store, and I hadn't used my membership at the point-of-sale terminal, I would have been able to essentially get away with the merchandise for FREE!! I can't imagine merchants would be too thrilled to accept Apple Pay at POS if they knew they might not actually get their money.

[Re-Titled By Moderator]