I was upgrading a few things on my lower this weekend and I accidently tipped the lower over and some sort of a detent came out. It's plastic and kind of thick. Now one of my takedown pins came completely out and the pin fits pretty loose. Should I assume that the detent goes into the hole where the takedown pin goes in and out? If that's where it goes are there any ideas on how to put it back in? Sorry for no pics. Late night, frustrated and tired.