I had to be away from my computer for a bit. Thanks for all your kind replies. It is indeed the left rear frame rail and it looks exactly like the picture that Butch posted. What I mean by it's not there, is just like in Butch's picture it appears like it was sheared off. I would think metal fatigue of the frame rail like SJ 40 said probably summarizes it the best. The S/N is ELG***US. The pistol has never been abused and I've always shot factory ammo. I'll call Smyrna, GA tomorrow and get the ball rolling. I have a few questions
1) should I send the frame with all the components or strip it?
2) for those who had the frame replaced how has having different S/N's for the frame and slide affected the value of the pistol.