Drop shadow settings.
Element of ContentTransparencySetting.dropShadowSettings
(a bit unexpected, but there you go.)
FillTransparencySetting appears to be "Transparency settings for the fill applied to the parent object.", as a property of regular objects (Button, EPS, GraphicLine, Image, Rectangle, TextFrame etc.), although to be sure you should check StrokeTransparencySetting as well.
Sorry to be posting to this thread after such a long stretch og time but its related to this.
In the Indesigns user interface I noticed that in the pages pallete, the page icon displays differently if it has a transparent object (It displays a gray chequered pattern).
Is it possible to use this somehow via a script
eg: If page icon display is chequered = page contains transparent objects