It is indeed not possible to find the Lisp manuals. Not in the help and not online.
This is what I see in the subscription center:
Downloads
No documentation anywhere.
The previous posts were from nearly eight years ago. Today, I am appear to be getting the same thing you got, and there does not appear to be a PDF download for the AutoLISP manual anymore. Autodesk has restructured the documentation and Help several times since the 2004 releases. The Autodesk Exchange site for AutoCAD does allow you to download a PDF of the main product manual, and there is also one on general customization. The AutoLISP one is not available there.
The 2004 release AutoLISP PDFs are too large to post here. There will not be anything on the CUI in them, and any recent revisions or additions to AutoLISP will also not be covered, so the on-line Help (AutoLISP Developer's Guide and AutoLISP Reference Guide) may still be your best resource.