If you close the Windows Vista Notes Gadget by mistake, you will lose all the important notes and reminders, which you may have made on the Notes Gadget.
Recover lost Sticky Notes
MVP colleague, Suvajit Pal, has suggested the following solution, to try and get back the notes.
If you have Volume Shadow Copy turned on and if you have a recent System Restore Point created or available, of a point, before you closed the Notes gadget, then look for Previous Version of the Settings.ini file for the Sidebar. You can do so at:
Anand Khanse is the Admin of TheWindowsClub.com, a 10-year Microsoft MVP Awardee in Windows (2006-16) & a Windows Insider MVP since then. Please read the entire post & the comments first, create a System Restore Point before making any changes to your system & be careful about any 3rd-party offers while installing freeware.