Ownership of files and quote. Hunting them down..

I have 9 users on an XSAN 1.4 each with quota. Although the majority of all the allotted quotes is in their FCP media folders, I suspect there are hundreds of gigs floating around there created from a multitude of different workflow scenarios going on.... etc, etc.

Since each file that counts towards the quota is "owned" by that user who was logged on at that point, I'm wondering if anyone has a script or a way to search and xsan volume for:
"all files owned by USER"

Thanks
Gary