Hi
Buddy, you ain't alone. I saw someone state LAST YEAR in June 2013, 'how can something with 24,660 views not yet be addressed?'. I mean, come on, it's just a note-taker, how complicated can they make it?!
My spouse lost her notes, and there is only one positive thing I can tell you:
Make sure you are NOT 'searching' for something on the searchline at the top when insode the 'notes' app, then you will see at the top, if you highlight any old note page you have authored, the word 'Accounts' will magically appear. Hit on this on the screen, and what ought to appear (don't ask me why!) is on mine, this -
All ipad notes
my email account one
my email account two
my.... etc
Notes on ipad only
So, trawl through ALL of these, by hitting on each one in turn - MANY people have found their 'missing' notes, under a different 'account'.
That's the end of the positive. If you have somehow sent a note to trash - it is gone. If it some how ELSE disappears, it's gone too. It's NOT your imagination, there is a glitch, thousands of people are not all wrong or explained by the 'accounts' solution alone. My spouse swears she did not hit 'delete' to confirm an accidental keypress, NOR did her notes appear having searched as above one by one the accounts.
PITA.
Best to all.