Articles are saved automatically at intervals.
For example, suppose you are called away from your desk in the middle of creating a new article. You don't expect to be away long, so you don't save. An hour later you come back to your desk to find your session has timed out. All that work lost.
Provided the administrator has turned autosave on, you can get your changes up to the last time the article was autosaved.
If you were creating a new article and had not yet saved it, you can see it on the Articles tab
If you open an existing article for editing and for some reason the article was not saved correctly, or an error occurs on the save, then when you next open the article for editing you will see the following message: