Hello Alok,
Ok, in that case you have to check the implementation class of the search result
Eg: CL_BUPA_IL_HEADER_SEARCH=>IF_CRM_BUPA_IL_QUERY~GET_DYNAMIC_QUERY_RESULT( )
In this method IT_SELECTION_PARAMETERS parameter will contain input search criteria.
You have to debug IF_CRM_BUPA_IL_QUERY~GET_DYNAMIC_QUERY_RESULT( ) and check where exactly the "WHERE" clause of the query is built and see if any BADI is available to change the parameter that is passed to "WHERE" condition.
Hope it helps.