TL;DR
If you pre-ordered a 6S device and paid with Apple Pay using an iOS 8 device and subsequently clean/DFU installed iOS 9 in "new mode" on that Apple Pay device on launch day -- check your order's payment status.
Talk about a brain fart. This is what I get for doing a pre-order via the Apple Store app with Apple Pay and subsequently clean-installing (DFU mode) iOS 9 on all my devices this week. Lesson learned.
Like many of you I pre-ordered an iPhone 6S Plus (and subsequently a 6S later that morning for The Wife) on pre-order morning/day. I used the Apple Store app and paid with Apple Pay, which as we know doesn't use the actual CC numbers but a "device account number" that is tied to your apple ID but is totally unique for each instance that CC is added to Wallet.
On iOS 9 launch day I did what I routinely do with major iOS releases: DFU installed the image and set up as "new". Prior to doing this I had logged out of my iCloud account on my iOS devices... which blew away any knowledge of my Apple Pay setup. Of course I set up Apple Pay again for the same CC in iOS 9 and got a new device account number. Any reference to the old one used for the 6S purchase was gone (as it should be).
Apple attempted payment yesterday 9/17 using the old Apple Pay info... which failed since idiot me nuked the device account number that was used for the orders. I had to visit the apple.com site and enter the CC payment info for it to clear which it did immediately, but remained in "processing items" status. Concerned delivery date might slip, I called Apple to check both orders and they're both still due to deliver 9/25. According to the rep my wife's Rose Gold 6S is shipping from a location within the US while my Space Grey 6S Plus is shipping from China. Without me asking her to do so, the rep added expedited shipping to my Plus order. Kudos, Apple. 🙂