Ancient thread, but you are looking for help rather than just adding "x2" to someone's comment.
So the bolt snapped? Not what you want to hear but you are going to need to take the grille right out so you can cut a hole in the bottom of the mounting surface. Then fish out the broken bolt and thread plate, replace the threaded plate and weld the access hole shut.
You might be able to do it with the grille in place by cutting the top of the mount open to remove the old thread plate but that depens on how much of the bolt is sticking out. Did it break off flush with the thread plate? Or did the head snap off?
'84 CJ-7: Yota axles (spartan locked front, e-locked rear) 4" BDS, 1" Daystar & 3/8" shackle lifts, 35" X-Terrains on steelies, YJ Tub & family roll bar, heater blower upgrade, 4.2L w/MC2100 & Team Rush, Warn 8274. Rebuilt 4.2/4.0 hybrid, AX15 and twin sticks/clocking ring waiting to go in.
The advertised position for a topless, dirty jeep girl has been filled......by my wife. Thanks to all that applied.
<------------and yes, that is her. :-D