Despite what Wikipedia may tell you, there is nothing preventing you from using scenario to refer to past events, especially if the actual circumstances are unknown or unclear: From NOAD:
scenario |səˈne(ə)rēˌō; -ˈnär-|
noun ( pl. -os)
a written outline of a movie, novel, or stage work giving details of the plot and individual scenes : imagine the scenarios for four short stories.
• a postulated sequence or development of events : a possible scenario is that he was attacked after opening the front door.
• a setting, in particular for a work of art or literature : the scenario is World War II.
Note that the last two example usages concern themselves with past events.