In Gospel Library Settings, turn on "Show Archived Content" – then you'll see the "Archived Content" section that caillines mentions, at the bottom of the Library.
If there are specific keywords she remembers typing in the notes, she should also be able to find them by going to Search, and choosing "Notes" on the first search filter. Personal notes aren't deleted, even when the underlying content may be modified or moved, but there's a lot of room for improvement in tools for finding older notes when content changes.
Samuel Bradshaw • If you desire to serve God, you are called to the work.