I'm fairly certain we can eliminate Versaille's Dictionary and Banknote. While a Dictionary is written, there is no way that a dictionary can be considered blank. And I feel like if the Banknote was the evidence, then Persephone would have said either Trading instead of Assembly or Loss of Valuables (insurance) instead of Nothing.
It's possible the Trophy could have been the murder weapon -- it would cause Severe Injury, be possibly found in the display case of a Cafeteria (although I would have gone for Classroom, myself), and hint of Action and Assembly in the form of sports events. The Numbers would still account for Written, Blank, and Nothing (zero).
The other outside possibility is James Moriarty's Blender and Note, although I'm at a complete loss as to what either of those have to do with Assembly. Perhaps some assembly required? I think I'm just stretching now, but I was so sure it was the Folding Chair. Meh.