What do you call those elements of a work of art which give evidence for events that occured in the mind of the creator, but not in the actual creation? For example, in "Barbra Allen", what do you call Barbra's accusations about Johnny Green's behavior at the tavern? The song starts in media res, in the middle of things, with poor Johnny already on his deathbed. Johnny's toast to the ladies does not occur in the actual song. The song contains "evidence" of the toast having "occurred", but it occurred only in the mind of the creator.   
I'm looking for a general term that would describe the bloodstains in "Edward", the wounds on the sculpted "Dying Gaul", the wet hair of the fleeing boys in Norman Rockwell's "No Swimming", and the "do do do so la ti do ti la so" of Mendelssohn's "Reformation Symphony". All of these elements are evidences of events which occurred in the minds of those creators, but which did not occur in the physical manifestation, the actual work of art. Surely there is a name for such "evidences". Thanks for your help!
Kent