I have been reading this thread with interest because when I uploaded my little book as an ePub created in Sigil I deleted every reference to the cover, including the file itself. The interesting thing is my book opens correctly and has a cover image when viewed in an e-reader.
So I have just gone onto Amazon and downloaded my mobi file again and used Calibre to change it into an epub which I could open and view in Sigil.
This is where it gets interesting, because the opf file I uploaded had no references to the cover but the opf I have extracted from the downloaded mobi file does! Clearly, in the conversion process Amazon has put in the opf the entries which were missing. They have also added the missing cover.jpg in the list of images.
It all works but I think I should probably go back and upload the epub again with the correct entries and cover.jpg file.
I can post the extra lines which have been added by Amazon if anyone wants me to - and I can work out how to post code here.
Edit: (just worked out how to show code)
This in the metadata section of the opf:
Code:
<meta content="cover" name="cover" />
This in the manifest:
Code:
<item id="cover" href="Images/cover.jpeg" media-type="image/jpeg"/>
And this in the guide section:
Code:
<reference type="cover" title="Cover" href="Text/titlepage.xhtml"/>
To reiterate, I did not have these lines in the opf file I originally uploaded, having deleted them. Amazon's magic elves must have added them.