revert draggable to original position

i´m trying to do this:
i have some draggable and some droppable
when i drag one of the to one drop i ask if you are sure, but if not i
don´t know how to revert the position, i try to change the option
revert but don´t do as i want
the code is as follow:
$(document).ready(function(){
        $("#browser").treeview({
            control: "#treecontrol"
        });
        $(".draggable").draggable();
        $(".droppable").droppable({
            drop: function(event, ui) {
                var drop = $(this);
                var folder = drop.find('tr').attr('value');
........
                var servicio = ui.draggable.find('tr');
                var origen = servicio.attr('folder');
                if(folder != origen){
                    jConfirm('Seguro quieres moverlo a esta carpeta '+folder,
'Confirmación', function(r) {
                        if(r){
                            // do some thing
                        }
else{
// revert to
original pos
}
                    });
                }
                else{
                    // do some thing
                }
            }
        });
thanks a lot