Albums Dissappeared Not in Deleted

Yes, unsyncing a synced collection in Classic will delete the album from Lightroom Cloud (there is a warning dialog that appears in Classic when you do that, did you not see or read that?). However, only the album is deleted, the images are not deleted (check All Photos to verify). It should be possible to resync those collections in Classic and they should reappear back in Lightroom. The only thing you may have lost would be any folder organisation in Lightroom, i.e. if an album that was removed by the initial unsyncing of the collection was in a Folder in Lightroom, resyncing the collection in Classic will create the album anew in Lightroom....but it would not appear in the original folder, so you would have to sort that aspect out manually.

If what you are seeing in Lightroom is different, we'll need to try to figure out the actual sequence of events. Start by telling us what the All Photos count is in Lightroom, and if that differs significantly from what you expected.