Get Attachment ID within Media Page Custom Field

Ok this is where I am right now:

I have the Attachment ID showing on the Media -> Edit Media Page using $_REQUEST[‘attachment_id’];

However the field shows up blank on the Media Library page within a post (which is where the id really needs to be seen)

In case anyone wants to look at the code itself here it is:

function my_image_attachment_fields_to_edit($form_fields, $post) {

	$form_fields["dl_page_media_field"] = array(
		"label" => __("Download Page URL"),
		"input" => "text", // this is default if "input" is omitted
		"value" => get_post_meta($post->ID, "_dl_page_media_field", true)
	);

	$form_fields["dl_page_media_field"]["label"] = __("Download Page URL");
	$form_fields["dl_page_media_field"]["input"] = "text";

//DISPLAY DOWNLOAD PAGE URL WITH FILE TITLE AT END
global $post;
global $wpdb;

//FIND ATTACHMENT ID
$attachmid = $_REQUEST['attachment_id'];
//END FIND ATTACHMENT ID

	$form_fields["dl_page_media_field"]["value"] = get_site_url()."/file-download-page/?download=$attachmid";
	return $form_fields;
}

// attach our function to the correct hook
add_filter("attachment_fields_to_edit", "my_image_attachment_fields_to_edit", null, 2);

Sorry about all the posts, I just want to keep updating with current place I am periodically when I make changes. The following is the cleaned up code (since the code above has a lot of fluff from trying things)

function dlp_add_custom_fields($form_fields, $post) {

	$attachmid = $_REQUEST['attachment_id'];

	$form_fields["dl_page_media_field"] = array(
		"label" => __("Download Page URL"),
		"input" => "text",
		"value" => get_site_url()."/file-download-page/?download=$attachmid",
		"helps" => __("Shows below new field"),
????);
	return $form_fields;
}
add_filter("attachment_fields_to_edit", "dlp_add_custom_fields", null, 2);