Word crashed and AutoRecover didn't save my chapter

Where Word may have kept it

Reopen Word before anything else. After a crash it usually shows a Document Recovery pane on the left listing what it rescued; open each item and save the one you want under a new name. If no pane appears, the files may still exist.

1. In Word for Windows, go to File › Info › Manage Document › Recover Unsaved Documents. The same button sits at the foot of the recent files list under File › Open.
2. Look in the AutoRecover folder yourself. File › Options › Save shows its path under AutoRecover file location; paste that into File Explorer. Files ending .asd open from Word's File › Open once you set the file type to All Files.
3. Search the whole drive for *.asd, for *.wbk (Word's backup copies), and for temporary files whose names start with ~ and end .tmp. Sort by date modified.
4. On a Mac, AutoRecover files live in a hidden Library folder. In Finder choose Go › Go to Folder and enter ~/Library/Containers/com.microsoft.Word/Data/Library/Preferences/AutoRecovery. Sort the folder by date; the newest files are the likeliest match.

Why it missed, and the settings to change

AutoRecover is not a save. It writes a recovery copy on a timer, ten minutes by default, and anything typed since the last tick is gone. Word also clears those copies away when a document closes normally, so a hurried click on Don't Save can take the recovery copy with it.

In File › Options › Save (on a Mac, Word › Preferences › Save), lower the interval to a minute or two and tick Keep the last AutoRecovered version if I close without saving where your version offers it. Under Advanced, Always create backup copy keeps the previous save as a .wbk. AutoSave proper, which saves continuously, needs the file stored in OneDrive or SharePoint.

In Tabularia

There is no timer to set. Tabularia writes each change into the browser's storage on your device as you type, and that stored copy is what brings the page back after the tab or the browser closes unexpectedly. With a Cloud subscription the same changes also go to online backup, and the saving indicator shows when this device has work still waiting to reach it.

Two limits are worth stating. A save can fail when the browser's storage is full, and Tabularia says so with Local save failed because browser storage is full instead of carrying on as if nothing happened. And on the Free plan the browser is the only place the book lives, so clearing site data or deleting that browser profile removes it; the guide on storage on your device covers persistent storage, which makes the browser less likely to reclaim it. For a copy that depends on nothing, export one now and then.