I sorry to hear about the situation.
I see you had a strange freezing issue here: Freezes When Clicking Search Button (Magnifying Glass)
I don’t think you replied there about this, but where is the Obsidian vault folder stored on your disk? Is it in a sync service folder (iCloud Drive, One Drive, etc.)? If a sync service isn’t set correctly to always keep a local copy of files and folders, it can move or change files under Obsidian’s nose causing issues (like disappearing or empty notes).
Looking at the debug info in the other topic, it looks like you have a Mac. Are you running Time Machine or any other backup system?
You could also try the core File recovery - Obsidian Help plugin, but I’m concerned the same could happen again even if you restored the notes. We need to get to the root cause of the issue.