THEME_alpha_preprocess_page(&$vars)

I try to refer to specific part in a region (a block in the custom region "region-copyright-second", like this:

$vars['page']['copyright_second']['block_15']['#markup']

But I get the notice error:

Notice: Undefined index: block_15 i THEME_alpha_preprocess_page() (row 17 of /home/.../sites/all/themes/THEME/preprocess/preprocess-page.inc).

The module Devel gives me this information:

...
copyright_second (Array, 4 elements)
    block_15 (Array, 5 elements)
        #markup (String, 306 characters ) <p>Webproduction: <span class="extx"><a class=...
        #contextual_links (Array, 1 element)
... 

What do I miss?