Scrivener sync lost my chapters. How do I get them back?

Before you open anything

Close Scrivener everywhere: every computer, and the iPad or iPhone if you sync with one. Then wait. Dropbox shows a finished state for each machine, and until every device reads up to date, opening the project again can write an older file over the one you want back.

That is also the rule Scrivener's own documentation gives for Dropbox in the first place. Close the project on one device, let the sync complete, and only then open it on the next. Chapters tend to vanish when a project is open in two places, or when a laptop wakes up and saves a stale copy before Dropbox has delivered the new one.

Where the chapters may still be

1. The binder itself. Search the project and look in its Trash folder. A chapter dragged into the wrong folder looks exactly like a lost one.
2. Scrivener's automatic backups. Unless the setting was changed, Scrivener saves a zipped copy of the project when you close it. The folder is named in the Backup settings: Scrivener › Settings (or Preferences) › Backup on a Mac, File › Options › Backup on Windows. Copy the newest zip from before the loss to your desktop, unzip it, and open that copy. Leave the backup folder itself untouched.
3. Conflicted copies. When two devices change the same file, Dropbox keeps both and adds conflicted copy to one name. Inside a Scrivener project those land among the project's own files, so search your Dropbox folder for that phrase. On a Mac, right-click the project and choose Show Package Contents to see inside it.
4. iOS sync conflicts. When Scrivener finds that a document was edited on two devices between syncs, it keeps both rather than choosing. The older copies go into a Conflicts folder near the bottom of the binder, marked with a yellow warning triangle and holding a folder named for the date.
5. Dropbox's own history. On dropbox.com, Deleted files lists removed files, and a file's Version history lists earlier copies. How far back either reaches depends on your Dropbox plan.

Once the chapters are back, take a manual copy as well: File › Back Up › Back Up To saves one to a folder you choose.

In Tabularia

Tabularia has no project folder for a sync service to carry. With a Cloud subscription it syncs the project itself. That removes the Dropbox step. It does not make two devices risk-free, and the guide on writing from two devices says how disagreements settle. If one device comes back from a stretch offline holding an older copy, the cloud's version replaces that whole copy, automatically. If two devices edited the same passage while both were online, one is fitted onto the other and nothing marks the spot.

The protection for a chapter is a Snapshot. Snapshots sit outside that replacement, so one taken before you left the desk is still there to preview or restore. Restoring saves where you stand first, under Before Snapshot restore, so going back is itself reversible.

On the Free plan none of this syncs. The book stays in the browser profile where you wrote it, and clearing that browser's site data deletes it. An export at each milestone covers that case on either plan.