My wife and I both had the same problem. I think it's Yahoo! I haven't found anyone with the same problem that isn't using Yahoo for their email account. By the way you can recover all your Notes by going to Yahoo mail. Note that there is a folder called NOTES. They should be there even if you lost them in your IOS system.
I'm been using Evernote. It has some amazing features and allows you to share notes with others. For example I have a wish list I keep and share the folder with my wife. Anytime we find something we like we jot it down in Evernote and it shows up in our Wishlist that we can each view. It even allows Hyperlinks to show them just exactly what it is you want.
Apple has complicated, a simple app in the iPad Settings.
If I want to store my notes on only my iPad Air, I have to disassociate
the Notes App from my mail accounts. Apple associates the Notes app
with other mail accounts automatically for whatever reason in iOS7.
Settings/iCloud/Notes - OFF
iCloud/Notes - OFF
GMail/Notes - OFF
Yahoo/Notes - OFF
(If you do all the above, the below will change to)
Settings/Notes/Default Account/On My iPad
I may go back and turn ON Notes to iCloud for backup,
but I don’t use extensive notes, so it may be a waste.
I keep the iPad Air regularly backed up/synced to my iMac anyway.
All the stupid syncing complicated this simple app.