The get_search_query() function was returning an empty string when used inside a Toolset View, causing the Relevanssi relevanssi_didyoumean() function to fail. The issue occurred because Toolset custom search does not use WordPress’s default ?s= parameter, so get_search_query() had no value to read.
Solution:
Instead of using get_search_query(), the Relevanssi function was modified to use the Toolset View’s search URL parameter. By passing the View’s actual search parameter value to relevanssi_didyoumean(), the “Did you mean” functionality worked correctly inside the View’s “No items found” section.