Its possible that the Revit file has an AutoCAD dwg which is actually jus linked and not inserted / added to Revit file. In that case, like u handle the Images in an AutoCAD file, same way u need to manage the links of the dwg file.
1 way wud be to copy that same AutoCAD file and place it on ur PC by creating the same folders along the same path name, and u must now be able to see the AutoCAD file in the Revit File. Try that out.