It's funny, I hadn't been keeping up with this forum in a while, and just happened to check it today, to see myself mentioned. Ixchel13, you did a good job of summing up my understanding: I'm under the impression that at 2:48 am (I don't remember where I got the exact times) Lauren and CR entered the infamous alley (between Tenth & College Apartments and Tenth & College Village Apartments, and exited the alley at 2:51. While in the alley, Lauren falls down and hits her head, and has to be helped to her feet. As I understand it, Lauren's exiting of this alley (presumably to immediately lose her keys on the nearby railing, and cross the gravel lot with CR, on their way to his place at 5 North Townhomes on 11th St) was the last time she was on camera.
I am fairly confident that ZO lived in Tenth & College apartments, because that can be seen in public records from the time. The fact that ZC lived at T & CV is inferred from the fact that Lauren and CR are supposed to have attempted to visit her on their way down the alley, which only seems possible if she lived in T & CV.
I found the FBI guy's discussion confusing in this video:
https://www.facebook.com/ABC2020/videos/10153980606204934/
He seems to be pointing at 10th Street, and calling it the alley. I think he must be confused. I believe the alley in question runs north/south between T & C and T & CV, as we've said. And what camera is he talking about, when he points to the law office across from Tenth and College? I think he must be turned around, and be referring to the camera in the alley. But that doesn't quite make sense, because he thinks that camera would have seen her walking home (which I guess could be true of the camera in the alley). Finally, at the end of the televised special, he hints that Lauren ended up partying at certain apartments, and points to apartments on Tenth St., across from T & C and T &CV. But if he's confused about the alley, maybe he meant to point to T & C? That would seem to make sense, since one of the apartments he pointed to wasn't even there in 2011, as far as I know.
He also mentions Lauren sitting down at one point in the alley. I don't know if there's a place to sit in the alley, or if this is a reference to her sitting on the steps of T & C, on 10th St., which just creates more confusion between 10th street and the alley.