Cloud sync deleted ALL my iPhone notes

I had notes stored locally in the Notes app on my iPhone.

Today, I thought it would be a good idea to back them up to iCloud.

I went to Settings and into iCloud, and then toggled to sync Notes to iCloud.

When I returned to the Notes app, ALL of the notes on my iPhone were deleted.

• When I switched on ‘Notes’ in iCloud settings, the phone - for some insane reason - automatically switched off ‘On my iPhone’ in Settings > Notes settings. Note that there was no pop up or warning about this.
• As a result of ‘On my iPhone’ being switched off, all my previous notes stored on the phone were automatically deleted. Again, for some insane reason.

After switching ‘On my iPhone’ back on, the notes are still nowhere to be found. They’re gone.

My recent notes are nowhere to be found. There’s no ‘Recently deleted’ folder, they’re not on the iCloud website.

They're gone. Forever, it would seem.

These were extremely important notes.

I would appreciate it if Apple could help me recover them.

Thanks.