I've had a number of instances where sellers who are crazy busy with tons of activity, inventory, etc, suddenly one day go completely dark. Whether it's inventory drying up, other priorities taking over, or other reasons, sometimes a seller just rides off into the sunset without warning, or no longer sells whatever drew you to them in the first place. Generally their profile will stay on the site for a while indicating no recent activity, but eventually eBay will close out the profile. I did not get any hits when I searched for blueyesman.
More importantly, if this individual is still actively collecting GPK, chances may be slim he'd be willing to part with whatever art you're interested in. Did you ask around on GPK message boards?