Photos disappeared from albums across all devices

iCloud (I assume) has removed all of the photos from three albums, one of which I’m using for a project. The photos were in a specific order (by date as well as in a before-and-after sequence) so they were easier to locate when uploading them to other apps. Thankfully the originals are still in the library, but now I have to start from scratch moving hundreds of photos into this album and putting them back into the correct order. 

I had just moved three photos to the album and reviewed which I would upload to work on in another app. Moments later, when I tried to upload them to this app, there were no photos in the album. They’re gone on all devices: a T7 external SSD (there’s not enough storage on my Mac mini M4; plus iCloud, if I understand correctly, isn’t supposed remove downloaded photos from external drives), late 2012 iMac, iPad Pro and iPhone 13.

I have a back up of the library on a G Drive, but haven’t backed it up in a couple of weeks. I assume if I do, it will remove the photos in the album there as well. The project photos are also individually backed up in a folder on a G Drive and a flash drive. Am I paranoid? Yes I am. I appreciate any help you can provide.