There are 2 options that will work as a n "Undo" feature to restore text  accidentally deleted in Co:Writer from your iPad.
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1.  The iOS device has a built in "Undo" feature for text you may have accidentally highlighted and deleted. Shake the iPad vigorously, like an 'etch-a-sketch' until the dialog box shows up to "Undo" or "Cancel". SELECT "Undo". This must be done immediately after you have deleted the work, Do not hit the home key or any other button prior to doing this. It sounds crazy... but it really does work!!

2.  The iOS devices OSK  has an "Undo" button in the bottom left corner of the numerical keyboard.