That is not a common failure but I am surprised that it made the pistol stop functioning. There are cases of people just trying to make a glock stop that the pistol got so hot the plastic rod melted and fell out. But the pistol kept working. I will post a link to one such video for you. As for the metal rod I have one in one of my Glocks. I don't see that it does anything the others don't do but then again I am not out there to try to tear up something like the people in the video were doing either. I think you just got a bad one. Put the new one in and don't worry about it.
The guide rod is noticed about 4:06 in the video this is a two part video and this is the second part. Video link: