I still can never get over the fact that Adnan has no idea, no memory, seemingly no recollection of what happened that day, that he thinks it was just an ordinary day. The police called him that night about Hae being missing! I know he was high, but wouldn't you stop and think, when DID I last see her? At that point it had only been a few hours and he should be able to remember that he asked her for a ride and she said no, or he didn't see her after school because he went to the library.
I realize there were a few days in there where no one was at school and people weren't really sure if she was missing or had run away. But once he had fixed in his mind when he last saw her, wouldn't he hold on to that memory?
When I was in high school -- 25 years ago -- a classmate was killed at school during lunch. I didn't witness it, I barely knew him but I have very crystallized memories from that day. I couldn't tell you everything I said and did, but that event suddenly made a regular day very abnormal and it sticks out. We went to Taco Bell after we were dismissed. I can't tell you about any regular day I went to get fast food after school but I remember that one.
It just seems like Adnan has no reference for the last day that he ever saw Hae, even though a lot of other people do. So I come back to he's lying or he has some sort of psychological block on those memories because of PTSD.