It's possible the offending shape is transparent or so small you can't see it. It's also possible the offending shape has been positioned outside the page area. Here is a macro that you can use with any of your documents. Basically, it looks for any shapes that are positioned to the left of the page boundary and repositions them so you can see them. It also makes very small shapes (height + width < 12pt) large enough to be more apparent.
Code:
Sub ShowShapes()
Dim Shp As Shape, Rng As Range
With ActiveDocument
For Each Rng In .StoryRanges
On Error Resume Next
For Each Shp In Rng.ShapeRange
If Shp.Left < 0 Then
Shp.Left = 0
Shp.ZOrder msoBringToFront
End If
If (Shp.Height + Shp.Width) < 12 Then
Shp.Height = 12
If Shp.Width < 12 Then Shp.Width = 12
End If
Next
Next
End With
End Sub
For installation & usage instructions, see:
http://www.gmayor.com/installing_macro.htm