In an Ask Google Bot episode, John Mueller answered the question - does a page need to be cached in order to appear in search?
To start, what are cached pages? Google takes a snapshot of each page as a backup in cases when the current page is not available and cannot be accessed. These pages then become a part of Google’s cache. If you access a cached version of a site, you will see the version of the site that Google has stored. If the website you're trying to visit is slow or not responding, you can view the cached version instead.
So does a page need to have a cached copy in Google to be able to appear in search? According to John Mueller – no, pages do not need to be cached in order to appear in Google search.
Cached pages are separate from indexing and they do not always reflect what is indexed. Some pages are not cached because of system design choices of Google’s infrastructure.
If you do not want your pages to be cached, you can use the “noarchive” robots directive.
Just because a page is not cached, does not mean that there is an issue with the indexing of a page. The cache is not required for search.
Check out the Ask Google Bot episode here: