Finally got it: it requires putting all 4 girls from the demonstration in the hospital to trigger the modified Rosario event in the afternoon. I guess that means the parasite is in one of those 4 and I look forward to finding out which.All memories can be unlocked, there are no future memeories to unlock so if you see the ??? you still have something to do.
As of version 0.19 you will have the orb that will help you track the parasite if you unlock contradictive memories of the behavior of a girl. For example Dana at the shopping mall
Cheers!
I have one last memory to unlock in v18.50: Cynthia, Day 3 Afternoon. This is related to the injured witness information but I already got that a long time ago and gave it to Cooper as previously, that was the only way to get to day 3. As I recall, I used a stolen dress from the Theater to get this but I'm missing the "you can use the explosion as a distraction" memory.
Looking at the walkthrough, it really feels like this is something I should have unlocked already ... Either way, I can't seem to make Cynthia ask me for a distraction again.