Why do my NOTES in iPhone 4S disappear?

I thought the notes were permanent and have lost some valuable info. Is there a way to prevent loss?

That's odd, it shouldn't happen. I tried it and even after quitting the app in multitasking it still showed up. Try testing the app out again and see if the same problem occurs.

His has happened several time to me. I enter notes and after several days I go back in and they are gone.