Hey there, and welcome to Apple Support Communities, sheake!
From my understanding, you deleted a note on your iPhone, and would like to see about recovering it. I’d be happy to go over your options with you.
It sounds like you’re using iCloud for Notes, so I’d recommend that you check your Recently Deleted folder using the steps here: If you're missing notes on your iPhone, iPad, or iPod touch - Apple Support
If you’re unsure if you’re using iCloud for Notes, you can check to see if any third-party accounts are synced by going to Settings > Passwords & Accounts, and checking to see if Notes is enabled for any accounts there. If so, you can log in to those accounts via a web browser and check the Trash folder to see if it’s located there.
You mentioned that you tried erasing your device and restoring from a backup already, so f you don’t see the note in iCloud, a third-party account, and it wasn’t contained within a backup, the note would be unrecoverable.
Kindest regards.