My library and its backup completely self destructed.
I do not use iCloud photos.
I've been using Photos/iPhoto app forever, so I am aware of how the preferences work, what "System Photos Library" means, etc. These Libraries were not system photos library.
I had all my precious photos in a library of ~300GB on an external drive.
Formatted as Mac OS Extended HFS+, mounted via USB.
I had it backed up to an SMB on a nas formatted as EXT-4.
I have been organizing the library over the past few weeks.
Two days ago I made a bunch of edits to the library on the USB (HFS+) drive. Then manually copied the library to the SMB share as I typically do after editing.
I watched the 300GB start transferring. It took the usual amount of time.
Today I go to work on the library on the USB drive. As has happened many times in the past, Photos surprises me with "Restoring" the library. It is ALWAYS doing this crap, either "Restoring" or "Updating" with no other info. Sometimes it takes 10 minutes, just a couple weeks ago it took more than a full day.
I finally get into Photos app and see 95% of my thumbnails are blank. Metadata is still there. Weird.
I go to the SMB share. Open the library. Photos goes through the same process. "Restoring" and blank thumbnails.
Open the library again, this time it's "Updating".
I see some recommendations online for restoring thumbnails like "rotate the pic" Doesnt work. It's not just the thumbnails, when I try to open the pic, its blank.
Glance at the library file, it is now 2GB, not 300.
"Show package contents" of library. There is no Masters folder. The originals folder is empty.
Assume its misreporting size. Duplicate library. Takes just a second. Its also 2GB.
Check backup. Its also 2GB. Duplicate. Its 2GB.
There's nothing in the system trash.
Ran Malwarebytes. Results: PUP.Systweak
I googled the results and people are mentioning an app called
Photos Duplicate Cleaner.app
I DO have that app installed from the App Store but haven't opened it in a month or so. It didn't offer what I wanted so I didn't even use it.
Quarantined and deleted it. Keep in mind I haven't touched that app in a long time. It's not in login items, I've restarted my computer many times since I last opened that app.