Hi kyle thanks for the answer, I have tried with this code:
RewriteEngine on
RewriteCond %{QUERY_STRING} ^id=13$
RewriteRule ^/page.php$ http://www.example.com/newname.htm? [L,R=301]
But it doesn't work. Is it possible that it requires page.php?id=13 to exist? I don't have anymore the file on the server... Trying to reach page.php?id=13 it responds with a 404 error.
Any solutions?