IPhone/iPad yellow notes the default app?

Can anyone tell me why although I have a number of notes in my yellow notes default app on my iPad/iPhone, the latest notes are disappearing into thin air after a few days, yet ones I added at the beginning are still there?

How can I retrieve my lost notes please? I use only one email account.

This is a very strange problem you have. Sadly you can't retrieve deleted notes. Has someone else been messing on your iPad/iPhone? Put a password just to make sure