> The question I have now is: where are the images?
Normally, on disk.

> They're not in any of the folders for the project.

Hmm, might have been deleted. The link may also refer to a non-existing file
(404, 500..)

> But there entries for all of them in the cache
> archive (new.zip).

Yes ; images will typically produce an empty entry, with meta-data stored in
the properties of the file (something unzip tools can not easily extract) to
locate the "real" physical file on disk, or to describe the error (404,
500..)