Here's the scenario: You are halfway through digitising a very large and complex feature, accidentally click too fast and invoke the finish sketch command resulting in a feature that is incorrect (i.e. self intersecting polygon). Pressing ctrl-Z deletes the whole sketch, replacing sketch doesn't always work*- what you really want to do is just go back to the sketch as it was just before you double clicked and continue digitising to finish.
Alternatively, you have finished digitising a large and very complex polygon or line but for some reason, ArcGIS has decided it doesn't like your sketch...sometimes for valid reasons (not that it tells you what the reason is) but sometimes it is something fairly simple to fix IF you could go back and edit the sketch.
As it is, there is no way to retrieve all that work in the sketch- You can either edit the accidental feature or start from scratch. So, please add the feature to 'load last sketch' or similar workflow
*'Replace sketch' doesn't work in a lot of cases, especially with self intersecting polygons as the last vertex is automatically added at the self-intersection point. Replace sketch doesn't also work when cutting a polygon (i.e. if you had done a very complex cut line but just failed to finish outside the target polygon. The cut wouldn't work AND you have no way of retrieving the cut-sketch to add the final vertex)
