2006 GP Rear Wheel Well Rattle/Noise

Something of a worn-strut-mount rattle has developed from the left rear. I can't see what else it could possibly be, but if I ride in the trunk (lol) I can "feel" the rattle just aft of the strut mount on the wheel well, but not actually on the mount itself or mount bolts. The passenger side does not have any sort of rattling. The dealer, of course, can't hear anything. Is it possible to have a worn strut mount after 30k miles? My Bonneville went 190k before the strut mounts went, and both at basically the same time. Any other ways to check if it is a strut mount? Any other possibilities here that people have had to deal with?