Puzzling Over Puzzling Over Presentism

Bill says,

When Boston's Scollay Square ceased to exist, it did not quit the actual world and become a merely possible object. It became a past actual object.

Hmmm.  When it ceased to exist Scollay Square surely became no kind of object.  Its individuality, its standing out, came to an end and it returned as rubble and dust to the undifferentiated bulk whence it sprang.  Consider, though, the knowledge of Scollay Square in the mind of someone familiar with it.  On learning of the square's demise this knowledge was not erased.  On the contrary, it became enhanced with one last fact:  that Scollay Square was no more.  But this can't be part of the content of the idea of Scollay Square---the properties it possessed, the events it participated in.  It must be a property of the idea itself---that the content applies to no object at all.  Neo-Meinongians will recognise an encoding/exemplifying distinction here.  Yet we still confusingly say that Scollay Square is a past object.  In a later piece Bill quotes Palle Yourgrau on the pictorial representation of the demise of Osama bin Laden,

Time maga­zine had it right when it represented the death of bin Laden, hence his 'nonexistence,' with a picture of him on the cover, crossed out with a big X. If you’re lecturing on the capture and killing of bin Laden, you might draw a picture of him on the blackboard, and then conclude your lecture by drawing, as Time did, a big X across that drawing. That would be the right thing to do. The wrong thing to do would be to simply erase the drawing, to rub it out. A blank blackboard does not represent the death of bin Laden. On the contrary, it represents nothing. Bin Laden, on dying, did not become nothing, just as he did not come from nothing. (Ex nihilo, nihil fit.)

What I think both Bill and Yourgrau miss is that both pictures are appropriate in different ways.  The erased board represents bin Laden himself, now nothing; the crossed out picture our idea of him.  Note how the picture contains a parallel semantic ascent:  there is content---the image of bin Laden, but then this is crossed out. The image remains and the cross is not part of it.  Bill continues, 

There are those who remember Scollay Square. Some of their memories are veridical and some are not. How is this possible if there is nothing that they are remembering?

This is perhaps more easily answered.  No one is remembering Scollay Square as it is now.  They are remembering it as it was when they were acquainted with it. 

What makes the veridical memories veridical? I will assume that we do not want to say that the past exists only in the flickering memories of mortals.  However things stand with the future, the reality of the past is near-datanic.

How can we know which memories are veridical?  Perhaps we can't, memory being less reliable than perception.  But we can be more or less confident depending on consistency among independent witnesses, photographs, documents, and other causal traces. Indeed, the past was.  We remember its being rather than imagine it.