In IPad OneNote accidentally deleted a section, how to recover back?
OneNote itself has a recycle bin, and deleted notes and sections can be recovered back through the Recycle Bin. The Recycle Bin is kept for a period of 60 days.
Open and login www.onenote.com, in OneNote Online, open the notebook, then click “View” tab -> “Versions” group -> “Deleted Notes” feature.
Here you can see the section you just deleted from your IPad, right-click on a page, and click on the "Restore" menu item to recover.