In my experience with floating shapes in the headers, VBA seems to think all the shapes are in every section even though the user interface shows a graphic only in one sections header. This can be further complicated when some headers may have 'Link to Previous' turned on.
So I have no faith at all in being able to use VBA to determine which shape you are referring to via the section number.
If you have some shapes in your document headers, try this macro to see the way VBA keeps track of these shapes.
Code:
Sub TestHeaderFloaters()
Dim aH As HeaderFooter, aShp As shape, aSect As Section
Debug.Print ActiveDocument.Sections(1).Headers(wdHeaderFooterPrimary).Shapes.Count
For Each aSect In ActiveDocument.Sections
For Each aH In aSect.Headers
For Each aShp In aH.Shapes
Debug.Print aSect.Index, aH.Index, aShp.Anchor.Information(wdActiveEndSectionNumber), aShp.AlternativeText
Next aShp
Next aH
Next aSect
End Sub
When I've tried to deal with this problem (years ago), I ended up using the AlternativeText to 'tag' the shapes I put into the header. Then I iterated through the shapes to find the one that had the Alt Text I wanted.