The package needs internal identifiers
DOCX separates document XML, relationships and media. When an image is inserted, Word assigns an internal media path such as word/media/image1.jpeg and links drawing markup to that path through a relationship ID. The original desktop filename is not required for the document to display correctly.
Why the source name disappears
Different Word versions and insertion methods preserve different metadata. Copy and paste, image editing, document conversion and privacy cleanup can remove or replace the name. A drawing description might still contain a candidate, but it is not guaranteed to be authoritative.
What an extractor should do
A responsible extractor uses a preserved candidate when it is credible, falls back to the internal name, sanitizes unsafe characters, prevents path traversal and numbers duplicates. It must never promise to restore information that the file no longer contains.