Losing the filename autotext from the header footer view is usually as a
result of replacing normal.dot with your own document template (only Word
can create normal.dot). However it is easy enough to resolve. Insert the
filename field into the footer and save the inserted field as an autotext
entry with the original name (filename or filename and path). This will
replace the original entry and make it available from the header/footer
toolbar.

The following macro added to a toolbar button will insert the filename and
path fields in the footer of the last page.

Sub InsertFilenameinLastPageFooter()
With ActiveDocument
   If Len(.Path) = 0 Then
           .Save
   End If
End With
Selection.EndKey Unit:=wdStory
ActiveWindow.ActivePane.View.SeekView = wdSeekCurrentPageFooter
With Selection
   .ParagraphFormat.Alignment = wdAlignParagraphRight
   .Fields.Add Range:=Selection.Range, Type:=wdFieldEmpty, _
   PreserveFormatting:=False
   .TypeText Text:="IF"
   .Fields.Add Range:=Selection.Range, Type:=wdFieldPage, _
   PreserveFormatting:=False
   .TypeText " = "
   .Fields.Add Range:=Selection.Range, Type:=wdFieldNumPages, _
   PreserveFormatting:=False
   .TypeText " "
   .Fields.Add Range:=Selection.Range, Type:=wdFieldEmpty, _
   PreserveFormatting:=False
   .TypeText Text:="Filename \p"
   .EndKey Unit:=wdStory
   .MoveLeft Unit:=wdWord, Count:=1, Extend:=wdExtend
   .Fields.Update
End With
With ActiveWindow.ActivePane.View
   .ShowFieldCodes = False
   .SeekView = wdSeekMainDocument
End With
End Sub

http://www.gmayor.com/installing_macro.htm

If it's available and you can insert it manually then that typically
indicates the style you are using in your footer isn't the footer style.
When your insertion point is in the footer what do you see in the Style
command on your Formatting toolbar?

Please post all follow-up questions to the newsgroup. Requests for
assistance by email cannot be acknowledged.

~~~~~~~~~~~~~~~
Beth Melton
Microsoft Office MVP

Coauthor of Word 2007 Inside Out:
http://www.microsoft.com/MSPress/books/9801.aspx#AboutTheBook