Missing Notes from Notes App on iPhone, iPad

The possible options are...

• Check in your iCloud account: https://www.icloud.com
• Check your email accounts that you had but removed. Because many of the accounts have notes synced like Google, iCloud, AOL, Exchange, Outlook, Yahoo etc.

You can't find it in the recently deleted folder, then probably you have not deleted any Notes in last 30 days.

(See the GIF below)

• ..

• You may have shared the Notes over AirDrop
• You may have sent the Notes via iMessage or email to someone
• Did you backup on Mac/PC via iTunes? Restore from iTunes. (Warning: Every step is IMPORTANT)

1. Locate Backup (~/Library/Application Support/MobileSync/Backup/)
2. Move the old iTunes Backup to a separate Folder / Drive
3. Take a fresh iTunes BackUp (Or else you will lose all new data, photos, Notes etc)
4. Now Move the NEW iTunes Backup to a separate Folder / Drive
5. Then Move the old iTunes Backup under ~/Library/Application Support/MobileSync/Backup/
6. Restore from Old BackUp via iTunes (Not iCloud)
7. Retrieve your Note(s) / iMessages / Photos etc...
8. Move the old iTunes Backup to a separate Folder / Drive
9. Now Move the NEW iTunes Backup under ~/Library/Application Support/MobileSync/Backup/
10. Restore from New BackUp via iTunes (Not iCloud)

Do not restore from iCloud backup.

iCloud backup doesn’t include information already stored in iCloud, like Contacts, Calendars, Bookmarks, Mail, Notes, Voice Memos, shared photos, iCloud Photos, Health data, call history, and files you store in iCloud Drive

Use Notes on your iPhone, iPad, and iPod touch - Apple Support

https://support.apple.com/en-in/HT205773