so this same thing happened again and i had to do a deep search and found the actual cause of this :
Just in WordPress 4.9 there’s this bug: https://core.trac.wordpress.org/ticket/42573 causing the template files to only be rescanned once every hour.
solution : ( till they release wp 4.9.1 and fix the issue )
Add the below code in child theme’s function.php file
function wp_42573_fix_template_caching( WP_Screen $current_screen ) {
// Only flush the file cache with each request to post list table, edit post screen, or theme editor.
if ( ! in_array( $current_screen->base, array( 'post', 'edit', 'theme-editor' ), true ) ) {
return;
}
$theme = wp_get_theme();
if ( ! $theme ) {
return;
}
$cache_hash = md5( $theme->get_theme_root() . '/' . $theme->get_stylesheet() );
$label = sanitize_key( 'files_' . $cache_hash . '-' . $theme->get( 'Version' ) );
$transient_key = substr( $label, 0, 29 ) . md5( $label );
delete_transient( $transient_key );
}
add_action( 'current_screen', 'wp_42573_fix_template_caching' );