> I'm wondering how large shops deal with the problem that when a filesystem
> is deleted from a client...

One way is to require that client systems do regular backups.
With that basis you can Query FIlespace at the server and in a
Detailed listing see when they actually did.  Anyone who hasn't
in some time may be contacted to see what gives.  Ultimately,
you can DELETE FIlespace for those too old to be viable.
    Richard Sims, Boston University OIT