Empty Drive from update?
A power surge isn't going to erase a drive.  Destroy it maybe, but erase the main partition while leaving the Recovery partition intact is virtually impossible.

If it was a power surge, the internal power supply would have been fried.  If that didn't fry the computer the greater than 18V DC along the power rails would surely have fried (at a minimum) the SMC (which operates on 5V and 3V DC).

What has happened is the user erased the drive in an attempt to bypass restrictions. I've seen my share of students who ask how to bypass restrictions both here and at many clients.  Here's just a short list of questions that fall into that genre:  


How do you download games on a school iPad?
Why does McAfee Endpoint Protection keep auto installing?
What is a organizational device considered to be? (This one is pretty benign but I have my suspicions...)
Amazon FireTV without WiFi, MacBook Pro Internet sharing
What websites can I use to get games in my schools IPad?


The only resolution you can take (and what I still do) is the following:


tell them "That's odd.  I wonder how that could have happened..."
proceed to put it in queue for repair
tell them that since they didn't have a backup per organization acceptable use policy (or similar) that their data is gone and the responsibility is theirs (you already indicated that)
document in writing with an email to the student


There will always be someone who wants to get around the system only to smack face-first into a brick wall.