Missing note entries from the app "notes"

I'm using iphone 4S in iOS 5.1.1

Recently I have found some of the memo notes from the app "notes" missing.

The no longer exist in the app, neither do they appear in spotlight search.

This is not the first time the problem of data lossing data from my iphone. This has occured since my iphone ran out of storage space.

But this time I'm having some of the important notes lost from the app, so I wish to recover them as many as possible.

Could anyone help me with this please?