Here’s a little Python snippet that finds all 3d objects that have View Visibility turned off. After you run the snippet, those hidden objects are selected, so you can open the Explorer and press E to see them.

import win32com.client
viewvis = win32com.client.Dispatch( "XSI.Collection" )
hidden = win32com.client.Dispatch( "XSI.Collection" )

si = Application

viewvis.Items = '*.visibility.viewvis'
for o in viewvis:
	if o.Value == False and si.ClassName( o.Parent3DObject ) == "X3DObject" :
		hidden.Add( o.Parent3DObject )

si.SelectObj( hidden )
for o in hidden:
	print o