Your real big problem here is the use of query_posts. It breaks the main query object, and sets the main query object to the query made by query_posts. What you are seeing is quite normal.
Your real solution here with the use of query_posts would be is to reset the main query back to what it should be. This is where wp_reset_query() comes in. If this is a normal page, is_search() will return false after wp_reset_query() as the main query is reset to the page’s main query.
query_posts( '&s=crap' );
// Do your loop as normal
wp_reset_query(); // Add this after your loop
var_dump( is_search() ); // Will return bool ( false )
Remember, use of query_posts is highly discouraged. You should be using WP_Query