When you go to the Detailed Question Breakdown and choose "Expand All", it tells you which essay questions are "Awaiting Response".

It says "Responses Awaiting: 1" (or 2, 5, 10, etc).

This should either tell you which students are still awaiting a response (for example, I've missed one student and now can't bulk commit my grades until I find out who it is. I will have to click on every student's results individually until I find it).