Help!

I was editing this article, to put an Interactive Diagram in the formerly empty Setup section, and when I saved it all other sections had disappeared. Fortunately I did still have the Introduction on the clipboard, but attempts to paste it back kept failing. I could paste it in the Setup section, and then it showed up. When I finally posted it in the Introduction surrounded by <p></p> tags it did get included in the page after saving.

Is it possible to check an earlier version to see what else was destroyed?