Backup mystery

I have used iPhones for many years, dating back to the first one. I currently have an iPhone 11Pro. It has always been set to store a backup in iCloud, and I check that every few months to make sure that the settings are correct and that nothing has changed.

Yesterday I had an issue and Apple tech asked me to do a factory restore. I checked the iCloud backup settings and everything was in the green, so I went ahead. Now, when I went to restore the phone in iTunes, it says there has NEVER been a backup of this phone. WTF????

Is there some mysterious step I need to take to find my backup? I upgraded to the iPhone 11Pro from an iPhone 7+ in November and it allowed me to backup from the iPhone 7 using an iCloud backup. Now it seems to show that I have no backups available whatsoever. I'm really annoyed by this and hope there's a solution that won't require me to restore everything manually.