Problem adding text widget to three registered sidebars

Hey there!

So I want to have three sidebars to display different content depending on the page. The first sidebar works fine. However, when I add the text widget to the second sidebar (or the third) and then reload the widgets page, the text widget is disappeared from the sidebar again. This is what I did:

functions.php

if ( function_exists('register_sidebar') )

register_sidebar(array(
  'id' => '1',
  'name' => 'sidebar1',
  'description' => 'Content will appear in the right header',
  'before_widget' => '',
  'after_widget' => '',
  'before_title' => '<h2>',
  'after_title' => '</h2>'
));

register_sidebar(array(
  'id' => '2',
  'name' => 'sidebar2',
  'description' => 'Content will appear in the right header',
  'before_widget' => '',
  'after_widget' => '',
  'before_title' => '<h2>',
  'after_title' => '</h2>'
));

register_sidebar(array(
  'id' => '3',
  'name' => 'sidebar3',
  'description' => 'Content will appear in the right header',
  'before_widget' => '',
  'after_widget' => '',
  'before_title' => '<h2>',
  'after_title' => '</h2>'
));

In sidebar.php

<?php if (is_page('2') ): ?>
<?php dynamic_sidebar( '1' ); ?>
<?php elseif (is_page('9') ): ?>
<?php dynamic_sidebar( '2' ); ?>
<?php elseif (is_page('11') ): ?>
<?php dynamic_sidebar( '3' ); ?>
<?php endif; ?>

and then I am calling the sidebar in the header with
<?php get_sidebar() ?>

Any idea what I am doing wrong? Why can I only add the text widget to the first sidebar? Basically, I can add the widget also to the other two sidebars but it won’t stay there.

Many thanks in advance!!