The game is set up so the student should start (more or less) where they left off. Since this is adaptive, depending on recent solutions, the game may back up and ask similar questions again but it definitely shouldn't start over.
That being said, it's certainly possible something didn't get saved. I'd need a few more details before I could even suggest a solution. Feel free to contact me at 425-312-3363 | firstname.lastname@example.org.
It's certainly frustrating to have to start from scratch. Please extend my apologies to the student and let her know I'll do my best to make things right.