Caching is just displaying what it got when cached. Was the service/result empty does it display empty as long as it is cached.
If i understand your questions correctly then the [ContentOutputCache] comes in the picture when you load the page but I think for your search purpose you should use the Object caching and I am not sure what logic you have written for fetching the articles.
We have [ContentOutputCache] attribute for News controller with setting of one day caching and we have call to search to fetch articles in same controller, if there is any issue with find service and it doesn't any result then results should be displayed from caching right?
Currently article result section is empty if there is no result from search.