Our car is an Australian Toyota GTS86 and does not have the pop rivet. Instead it has an upward pointing stud moulded into the bumper plastic near the indicator light (arrowed in photo below). The stud in turn locates up into a hole in the body metal. CORRECTION Nov.2013... our car SHOULD have had the pop rivet but it was missing. The upward-pointing stud mentioned is an additional locating feature i.e. not "instead" of the pop rivet.
Cover your bodywork paint. Via the wheel arch you can lever the stud down with a covered screwdriver to release it and pull the bumper away with the light intact.
In the photo the stud is arrowed. The light is only shown unclipped so you can see that pesky clip. I have now managed to bust that clip while struggling to refit grrrr
http://*************/forum/f26/bumpe...909/#post46333