I had a problem in DOCX where I have a number of documents containing the same image, sometimes many times. What I needed to answer is whether my documents CONTAIN the image, or whether all images were under LINK (as desired).
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NOW. This is EXTREMELY RISKY, as it appears you can destroy your document by playing in this sphere.

1. Backup your document to somewhere safe
2. Copy your document, creating '<document> - Copy.docx'
3. Rename your copy by appending .zip (this asks questions, but making it appear as a ZIP file is what you are doing)
4. Open the ZIP file using WinRar (other zip utilities may work, but this is my preference)
5. Select the subfolder within the zip called 'Word'
6. Select the subfolder within the zip called Media
7. There you see the list of INCLUDED media files.

And there I found the answers to what I was looking for. I could double-click to see which pictures I had inadvertently included.
MORE:

1. Go back to the Word subfolder within the zip
2. Select the _Rels subfolder
3. Double-click the document.xml.rels file. It should appear in your browser
4. Search through that for Target="file
5. That shows all the embedded files.
6. If you are REALLY-REALLY-REALLY game, open
   document.xml.rels in your favourite text editor, change as needed, and save back into the zip.
7. Reverse the rename so Windows thinks it's a Word document again.
8. Hope and Pray that you haven't destroyed your document

MORE:

1. Within the document.xml.rels file, you find the picture that you want to find. Where is it in the document?
2. Check the reference in the xml. What you are looking for is the Id. Something like Id="rId18"
3. Go back to the Word subfolder within the zip
4. Double-click document.xml (which should open in your favourite browser)
5. Search for that id rId18
6. Somewhere near that should be some text that you recognise.

WHAT CAN GO WRONG?
Anything and everything. Like I said, this is EXTREMELY risky.
One that I noticed is that if you replace a picture with one of a different size then it is NOT resized in the document. It is shaped to fill the original space in the document.
BTW that is also true outside this workaround, where if you replace a picture of your wife with one of your children, and they are of a different size or aspect, then the end-result can be NOT what you expected.