Interesting choice of dates/events to use for the story, I'll grant you that. Wonder if someone just teleported away the posters though The concept is intriguing, and might have potential in a larger story too.
I do feel that a bit more could have been made about the mystery behind the posters. For instance a bit more setting up of the mood of reaction to the posters rather than just statements that group a said this, group b said that.
A few other notes.