I don't know of any way to filter under defined sketches directly. Maybe someone could write a macro to do it, but I don't know enough about them to know if that's a possibility. If no one else answers in a day or so you might try moving this Discussion to the API section. The macro folks would be more likely to see it there.
I'm not sure either, but if you haven't renamed your sketches, you could use the search filter in the feature tree. Just type in 'sketch' and all of the sketches will show up and you'll be able to see the state of each, without expanding manually. Otherwise, if this is a behavior you'd like to avoid in the future, go Tools>Options>System Options. On the System Options tab, select the heading Sketch and among the series of checkboxes on the right, there will be 'Use Fully Defined Sketches'.