Makes sense. At a public event I tend to chat with those around me (the family gives me grief for that). I wouldn't remember a face either but if I were shown a photo a few days later I might. The time span between the game and when she was reported missing was brief enough that the memory would still be recent.
I'm a chatter, too. But the pictures of JC I have seen all look different, so I can be pretty sure if he was there, I wouldn't have known for sure. We obviously don't know how well IL resembles her pictures. Unless they chatted with people around them about something meaningful, I can't imagine I'd really remember, either.