Some thoughts:
I doubt the school would start looking through ARP cache or any networking information without some legal intervention. You get into all kinds of sticky problems here ranging from privacy issues to resource allocation (who gets billed for the IT person's time). I work at a university and anything anybody does has to be billed to a group/department/task. However, the legal issues will most likely stop you.
Do you actually know your MAC address?
I would contact the police as the first step (both campus and area police).
I would suggest to them that the university might be able to track your laptop via networking solutions like ARP. They may be able to go to the university on your behalf.
If the university does not want to help you could contact an attorney to help you request the information. This may sound expensive but most decent colleges have attorneys you can consult for free (no kidding). We do as well as IU, PU, BS, and many others I have been at. I would contact my student government and inquire about free legal advice for students, they can probably point you in the right direction.
Lastly, be prepared to offer proof of ownership. Theft and ownership is another sticky situation. Having a credit card bill, receipt, or some other type of evidence goes along way. Put yourself in the position of the police here. If you accuse another person of stealing your laptop but they claim they have no idea who you are and have always owned this laptop, how to you tell who is lying?
Browsing the files on the computer will require a search warrant I believe so something with the serial number is your best bet.
Good Luck!
-P