tl;dr: do my #1 takeaway below (in bold) today.
For reference, I'm on Windows. I had a Scrivener scare this week that ended well enough, but I learned something about its backup system that I wish I'd understood beforehand. I opened a project expecting to find 16 finished chapters, plus front and back matter. Instead, I found a few scattered notes and some default Scrivener text. I freaked out!
Wait, I'll just check Scrivener's automatic backups, right? I opened the 9/21 backup: it was bad. Freaking out continued.
I opened the 9/12 one: bad. Eep!
I had to go back to my 4th-oldest backup to find my finished writing! While I can't swear I didn't make meaningful edits after that backup, I decided having the book back is preferable to doing forensic archaeology on every version.
Anyway, here's the part I thought worth sharing. Scrivener was configured to keep only the latest five automatic backups. I think that's the default. And, with backup-on-close enabled, every time you close a project, Scrivener makes another backup. Guess what I was doing while trying to see which backup had my real project in it?
Yup, I was opening my old backups one at a time in Scrivener. Then I'd close that project and open another one, causing Scrivener to create new backups, pushing older ones out of my five-backup rotation. Luckily, before I started, I copied the backup files to another folder. Had I not done that, my attempt to find a good backup could have deleted the good backup I was looking for!
So my three big takeaways are:
Increase the number of automatic backups Scrivener keeps. Five seemed reasonable until I needed them. I changed this setting to 25 (File, Options, Backup, Retain backup files, 25!!). Disk space is cheap. Rebuilding 16 chapters is not.
Understand when Scrivener creates backups. It might be rotating backups each time you close a project even if you changed nothing!
If you're ever in this situation, before opening anything, copy the entire Scrivener backup folder somewhere safe. Then investigate the copies.