I think you found the answer you were looking for by answering our own question but if you want to use codeigniter to get all rows except for the first 10 then you would need to do something like (I have yet to test it):
$this->db->limit(18446744073709551615, 10)
According to Mysql Documentation
To retrieve all rows from a certain offset up to the end of the result set, you can use some large number for the second parameter.