When the cars were produced, they were produced with ball joints which had a screw-in plug in the ball joints, like a small bolt screwed into the hole where the grease fittings were later installed. The FSM said to remove the plug, install a grease fitting, and grease the ball joint when needed. THEN remove the fitting and re-install the bolt/plug afterward. This way, no contamination could enter through that hole. Which made sense . . . UNTIL you realize that the grease fittings all had a spring-loaded ball to keep them closed when not being greased . . . AND no lube tech would go to the trouble to remove the plug, install a fitting, and then remove the fitting and put the factory plug back into the hole. Doing things as the FSM indicated was also protection against any sub-standard grease fittings being installed, too. So the default mode was to keep the ball joint with uncontaminated grease in it, according to the factory people.
But what really happened, even at the dealerships when the cars got their first lube job (whether at their first oil change or at the 36K interval), was that good quality grease fittings were installed and left there, in place of the factory plugs/bolts. IF the grease fittings got broken off, their threaded portion should still be in the joint, with a hole in the middle, which should be obvious under all of the accumulated stuff on the joint, over the years. There might well be a picture of the ball joint with the plug in it in the FSM front suspension section?
Enjoy!
CBODY67