I have recently started using the new Lightroom CC, and all was working fairly well. However, i happened to start Classic, and it started syncing all my cloud library because there was a collection set to sync with LR Mobile. Didn't want this to happen, so I deleted the collection - without thinking about the consequences! Basically, all the photos in the cloud library were deleted in the process of deleting the collection. Of course, when I started the new CC again, it too synced and deleted all the photos. Disaster!
Now then, I can restore the whole CC library from a Time Machine backup (fortunately, I have CC set to hold a copy of all originals). But as soon as I start CC, it syncs and deletes all the photos again, I guess because the cloud has the "truth". How can I get my photos back? There doesn't seem to be a way to override the sync behaviour. If I turn off my internet connection after the restore, I can see all the photos, but as soon as the Internet is back on - whoosh, they all disappear.
I ended up restoring the library and starting LR without an Internet connection, so I could see all the photos. Then I used "Save to" to export originals+changes for each album individually. Then enable Internet, photos all disappear, then re-import everything. Of course, they have to all sync back up to the cloud. Laborious, but it worked...
Great stick-to-it-ness here. Thanks for the update too as it may help others encountering the same problem.