If you have a Yahoo mail account as your default e-mail, and you find your 'Notes' have disappeared after sync, check your e-mail "My Folders" box for a folder labeled "Notes".
All of your notes should be there.
To turn off iphone Notes from syncing:
Steps:
1. From iPhone select Settings > Mail, Contacts, Calendars > Accounts: Yahoo! > Notes - slider "off".
For more information, see here.
