Kinda surprised this even needs to be said, but not only did I fall victim to this, so did one of the people in the Adobe training videos! 🙂
When you go to edit a sketch, tht sketch should always be made initially visible. This should be the case even if the 'All sketches' node is hidden. Sure you could re-hide it when you were in there (if you wanted to) but by default, it should be made visible.
Currently, if your 'all sketches' node is hidden and you go to edit a sketch, you end up with a blank screen and a confused look on your face. You've already said you wanted to edit that sketch so making it visible can be a safe assumption.