I don't think it was active investigation. The files were closed when communication stopped, and then no further action was taken.
That isn't actually what the investigation was supposed to do. The investigation was supposed to identify whether or not the person was complying with the terms of their study permit. In this case, it would mean studying full-time. It's very likely that there are some who are genuine students, and they need to be given the opportunity to demonstrate that. However, when they're not, then an action should be taken.