My Notes stored in iPhone storage (not iCloud nor Gmail) was gone with no reason. How to restore it back?

Hi easysonon,

Welcome to the Apple Support Communities!

We understand that you're unable to locate any saved notes on your iPhone. We see that you've already reviewed "If you're missing notes on your iPhone, iPad, or iPod touch" which is a great place to start.

If you're unable to locate the missing notes in the Recently Deleted folder or in any other accounts that are associated with Notes, or by searching for them, we'd recommend that you restart your iPhone first. If you're still unable to locate them, you can also try to connect to an alternate network then search for your missing notes again. For example, if you're currently connected to a Wi-Fi network, connect to your cellular network instead and search for your notes.

Do you have a backup of your iPhone on your computer since you don't use iCloud? Another option would be to restore that backup. Keep in mind, if the backup was created earlier, any data saved on your iPhone since the last backup will not be included in the restore. This article will guide you through the process: Restore your iPhone, iPad, or iPod touch from a backup

We hope this helps.

Cheers!