iPhone has a default "Notes" app which allows us to store notes. Stored notes can be deleted by hitting the "Delete Note" button:
How do we recover a note that is accidentally deleted?
Is there anyway to undo the delete?
The linked app works only for Mac, but here's two alternatives (not tested) :
There is a way to undo the delete. You just have to shake your iphone, and this will activate the "undo" feature which seems to have been forgotten by most people (it was a feature of an iOS update a few revisions back around 2009).
In case you think I am kidding, click here.