I wouldn't rule out a forum member spotting it . If they've got the keys they are probably going to be driving it around. All Zed owners are constantly looking for other Zeds, so its just a matter or time, (unless they hide it, strip it or export it )
So its 2003 Grey 3.0 roadster : Reg YL03 HCA In the Nottingham Area.
Why don't you Bold it in your OP, or even put the Reg No in your Post Subject title ?
Good luck with the outcome. (I'm not sure if I'd want it back ranted and abused, sometimes I think I'd rather have the money and start afresh).