How to recover missing notes since Mavericks update?

Very recently I've updated my computer via the Mac App Store to Mavericks. Today when I opened Notes I noticed the background had changed but even more startling was that all my notes were gone! It shows "error 43".

I have an external hard drive and backed up my computer.

Is there any way to get my notes back?

The notes should be stored in your backup, at least. Check here

Solution is to navigate to ~/Library/Containers/com.apple.Notes/Data/Library/Notes and restore:

NotesV1.storedata
NotesV1.storedata-shm
NotesV1.storedata-wal

Where ~ is your home directory e.g. /Users/your_username

Refer macrumors or apple discussions for more info.

This should fix the problem:
Note: If you do not have an Apple ID, that means your Notes are completely lost.

1. Go to Finder.
2. Click on Applications.
3. Find System Preferences.
4. Click on iCloud.
5. Log in to your iCloud account if you have not logged in yet.
6. Select the Notes checkbox.