This article explains how to replace the native search bar in the Bigcart theme by C-Themes.
FiboSearch plugin has built-in integration with the Bigcart theme. It means you can replace the default search bar by selecting a single checkbox.
If you have activated Bigcart theme or child-theme of Bigcart, you should see the following screen in the plugin settings:
WooCommerce -> FiboSearch -> Starting (tab)
Select the option “Replace all Bigcart search bars with the FiboSearch.” and the search bar should be replaced.