Nielsen is an awesome role model but I’ve always had a peeve about Nielsen’s # 9 Heuristic - Error Recovery - Help users recognize, diagnose and recover from an error. I think it’s added as a filler so the Heuristics could be rounded nicely to an even 10.
Is it not simply a combination of Heuristic #1: Give Feedback , #2: Speak User’s Language, #3: Allow Users to Undo or Escape from Mistakes or undesired actions and #5: Prevent errors through design?