Notes disappeared in iphone and icloud after an update

Re: recovering notes

Apple Support's online article: Use Notes on your iPhone, iPad, and iPod touch - Apple Support

Says

"To recover a deleted note, go to the Folders list and tap Recently Deleted. 

Tap the note that you want to keep, tap in the note, then tap Recover."

and

If you're missing notes on your iPhone, iPad or iPod touch – Apple Support

says:

If you store your notes on iCloud, check your Recently Deleted folder:

Open Notes, then tap the back < icon  until you see your Folders list.

Tap Recently Deleted and search for your note.

If you find your note in Recently Deleted or in another folder, you can move it:

In the Notes list, tap Edit.

Select the note that you want to move.

Tap Move, then select the folder you want to move it to.

If Recently Deleted folders are no help:

The only other opportunity of recovering notes is from a back-up you may have, if you have one that includes notes

Eg" You may have complete iPhone back-ups on an external jump drive / hard drive / computer

What does iCloud back up? - Apple Support

says:

"Your iPhone, iPad, and iPod touch backups only include information and settings stored on your device. 

They do not include information already stored in iCloud such as "Notes" .......  (etc.).

If needed:

iCloud Support Team:

iCloud Support

or

iPhone Support Team

iPhone - Official Apple Support

(NB: (There's a "Get Support" link at the bottom of both webpages)

All the best :-)