• Change your word file extension from .docx to .zip
• Go into the .zip archive and open file word\document.xml with any text editor.
  
  
  
• Look for any text that was close to the image in question an somewhere around you should see XML code similar to
  <pic:cNvPr id=”0″ name=”Test image.png”/>
  
• In this case Test image.png was the name of the original image
  
  

MS Word 2010