With burners they would still need to be very clever if they were ever investigated for this. The coaches would still need to call their home or legit cells to show a record of calls made to the recruit that was legit. The NCAA could still request their phone records and if there were not any calls from UM coaches that should raise some eyebrows. I honestly doubt any of those coaches are clever enough to make calls to their homes then call the burner too. Maybe the burner was used during the dead period or when calls were not allowed.