A new guy's 2 cents:

I know I'm new here, nor am I a lawyer, but I have done a LOT of reading about copyright law as a result of a parallel incident.

Posting something on the internet does NOT make it public domain unless you explicitly say so. If you created it, you have full copyright from the moment you create it. The only exception is if you post it somewhere that the act of posting gives someone else rights over it.

In your shoes I'd go directly to the head of the unit, via telephone if possible. They may not know it is stolen.