Not just this plugin, but no search plugins will work if there is no post content available.
Visual Composer works because it stores the built data in the post content (within shortcodes) and not somewhere else. I believe most “content builder” plugins do the same – because it would break the default wordpress search as well.
The search is even a Visual Composer addon itself: http://vc.wpbakery.com/addons/ajax-search-pro/
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