Assuming that this is more of an aesthetic issue than security, here's a quick solution that you can use to hide any page in the Pages tab using CSS:
Add that code into any plugin of your choice and append the $hidePages array with any other page slugs that you wish and they will be hidden from the client.
Code:
$hidePages = array('gallery');
add_action('header', 'hidePagesOnPages', array($slugs=$hidePages));
function hidePagesOnPages($slugs) {
echo '<style type="text/css">';
foreach ($slugs as $slug) echo 'tr#tr-'.$slug.' { display: none; }';
echo' </style>';
}
Add that code into any plugin of your choice and append the $hidePages array with any other page slugs that you wish and they will be hidden from the client.