I gave a quiz to 50 students, new style type and everything went  fine, or so I thought. 

When i checked one student's log (from the Moderate tab), instead of showing their quiz activity I get

There are no session events to display yet.

What could have gone wrong?  Any chance the student hacked in to enter answers?  Their score was rather low, and I doubt this student is a computer savy hacker but someone else could have done something for them or to their account.  or maybe they answered on their phone and the phone log is not supported,.