Use the search functionality to search for "tim smith csh callan". You get one result, which is a 2007 post from comp.os.linux.advocacy where someone is quoting a 1984 post of mine that was in net.unix-wizards. Note that my 1984 post is not found.
Now go to the Google Groups version of net.unix-wizards [2].
Search there for "tim smith csh callan". Now the above mentioned 1984 post is found, along with another 1984 post.
Lest you think that there is some problem when searching from the main page, click on the "Search all groups" link on the net.unix-wizards search results page, and it only finds the 2007 COLA post that quoted my 1984 post.
A search from the main Google search page, as opposed to the search within groups, finds the first 1984 post as the first result.
I've seen vast numbers of posts become unfindable by search, and then weeks or months later become findable again. For instance, there was a long time when if you searched for "Bill Gates" in Google's usenet archive, it would only return something like a dozen posts.
To put it bluntly, Google's handling of the usenet archives has been negligent and/or incompetent.
[1] https://groups.google.com/forum/#!overview
[2] https://groups.google.com/forum/#!forum/net.unix-wizards