I was installing a new Timney trigger in my SCAR today, when I noticed a strange bolt in the front left corner of the lower where the mag seats in the top part. It looked like a bolt that had been ground down from the factory and I noticed that my buddies scar had it too but mine had come unseated in my gun after firing it a lot yesterday. Should I glue or locktite it back in place? What the heck is it? Thanks!