If there is a "zombie" system in LC it is not easy to track it down. On querying the recipe, the system should upload some basic info about itself - at least ip addres and MAC address and may be be other HW info.
Could this also be a workaround to the issue of virtual guests not being assigned their intended IPs? As it is, virtinstall test machines aren't easily reachable. It would be nice for them to "phone home" so you can find where your guest recipes are running.
*** This bug has been marked as a duplicate of bug 655009 ***