The "can't turn in quest item" glitch is, unfortunately, extremely well known. Here's what happens:
There are items necessary for radiant quests. A radiant quest is one wherein you can be sent to one of several locations to find the item; it is not scripted to be in one place every time you play.
There are items necessary for radiant quests. A radiant quest is one wherein you can be sent to one of several locations to find the item; it is not scripted to be in one place every time you play.