First of all, I hope the person has stopped using the drive at all before this recovery process is attempted. We don't want to write over the file.

I'm not sure exactly how this drive is networked, but this program claims support for networked drives. I don't know if this program does, but it seems to be one of the more popular apps for file recovery (I just snagged it, as it's free at the moment).

A couple others that you may or may not have stumbled across can be found here and here.