Puzzling, no?

Was gifted this fab puzzle featuring Nancy Drew book covers spanning the series from vintage to newer. Super fun but got to the end to find one piece missing. Probably an innocent factory mistake, but I couldn't help wondering if it was someone's idea of a joke to drive puzzle doers mad. Of course I'm a mystery writer so I'm suspicious of everything;)

Totally fun, though, to see these old covers and got me remembering the stories and which cover editions were on the books I read as a kid. I remember loving The Hidden Staircase but mine didn't have that cover. Anyone else recognize any?