You don't have to purchase expensive apps or go through complex procedures; iOS 9 is shipped with a revamped version of the Notes app that keeps your deleted notes in a special folder. Deleted notes are kept for a period 30 days before they are permanently erased.
How To Recover Deleted Notes on the iPhone, iPad and iPod Touch
Open the Notes app and then tap on the small < button to switch to Folders view. Go to On my iPhone > Recently Deleted. All the notes you’ve deleted during the past 30 days are listed there.Select the desired note and then tap on the Edit menu > Move to…. Transfer the note back to your main Notes folder or iCloud.
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