Restore from iCloud Backup lost ALL my photos — Ideas? On Saturday I got a new iPhone X 256. Previously I had an iPhone 7 128, which I backed up in the AM, and again at the store just for good measure. Everything in iCloud was set to "On." Both backups took under 5 minutes.

As expected, we chose Restore from Backup, and once my apps and whatnot started populating on the iPhone X, ATT wiped my iPhone 7 and sent me home.

The next morning I opened Photos and now they only go back to May 25, less than a month. On my old phone, they went back to 2010, and there were thousands. All photos on my new phone appear to be in photostream, the Camera Roll is showing 0. None of my Albums loaded (except Photostream). Everything else on my phone appears to have restored perfectly, Chrome even has the same tabs open that I had on my old phone.

I called Apple Care, and though they "escalated" my issue to the engineers, I've been told they were unable to recover any photos from my backup files.

When I wipe my phone and go to Restore from Backup, I have 3 options available: the one I used, one from 2 days earlier, and one from the day before that. I was told by Apple Care that all of these backup files are around 2 GB (i.e. they don't contain photos). They said they were "Snapshot" backups, which means that they are new files created since the large backup. When I asked if I could backup from the large backup file, they gave some very vague answers and said that they do not see that file. When I look on my computer at iCloud > Devices > Choose iPhone 7 > Backups, there is an additional backup of 22 GB that has no date and has (incomplete) next to it. Presumably this too has no photos, since there should have been about 80 GB worth of pics. But maybe there are some?

I haven't backed up to a computer since May 2016. I'm going to try restoring to that file to see if I can recover some photos that way, and maybe "only" lose 2 years of memories.

What else can I try to recover these missing photos?
I recommend restoring those backups. 
iCloud Backups are compressed to save memory. Just because they show lesser GB than the full amount of your photos and videos may have, doesnt mean that they arent there. Also backups are done over time, so the photos and videos are also saved over time, never all at once.

I would restore from a backup and see what you have. Also when the latest backup was installed, did you have iCloud library turned on in iCloud settings? If so did you have optimize storage turned on? You'll want that off if your iPhone has enough storage for your photos.

And lastly make sure you go to www.iCloud.com since all photos that iCloud can send to your iPhone will come directly from there as well as your backup. See if you can verify that before giving up on the backups.