Hittest removemovieClip

onClipEvent (enterFrame) {
	if (_root.btn_1, hitTest(_root.head)) {
		_root.attachMovie("main", "main_mc", 60);
	
	} else {
		_root.removeMovieClip("main_mc");
	}
}

the attaching movie work, but why doesn’t removeMoveClip works when it doesn’t collide anymore?