When I went to look at the work of 3 students (out of 24) in Unit 3 Lesson 10, there was nothing there. It looked like they had never started the lesson but I know that they did. As it stands right now, they have lost all their work. It also showed no version history. I checked all the different lessons, too, to see if anything was there but there was nothing. Has anybody else had this problem?
Since you already checked older curriculum versions, I would check if these students are using the same account that they used to sign up for your class. If yes, contact firstname.lastname@example.org with the student names.