Common sense suggests such is yet to happen. Airmanship requires an understanding the risk in aviation is greater than absolute zero, which is okay as long as it is managed reasonably.
The non-etops rule assumes that on a day of
- a real engine failure, single side
- to an aeroplane flying non-etops over austere places
- which happens at the most critical point of the route
- on a day when the closest field is available but not suitable
==== there's at least one pure soul worth saving onboard, so that ======
+ the remaining engine will not fail from independent causes in less than 2 hours (for the 60 mins-distance rule)
The four 'minus' probabilites above multiply, resulting in an effective nil chance of being that unlucky. Even if, then frankly engines don't fail in the cruise much at all. Take-of and climb cases are well covered by the TKOF ALTN requirement, the same principle applies for G/A at the other end. Applies for the remaining engine as well as for the first one to fail.