Originally Posted by ScottS

Well said, and this is my actual experience. After my spring slipped past the nut on the front of the guide rod, seemingly trying to leave the area altogether, I was able to get it back into the slide (through clever redneck engineering), and after doing so, the gun functioned flawlessly for another hundred rounds or so until it was replaced. I have every confidence the gun would have continued to function without a problem, since (like Rastoff mentioned) the spring is essentially "captured" by the slide in a way somewhat similar to other, non-captured designs.