The error means it tried to create an adoptable with the ID 9 from the database and it didn't exist. It doesn't mean necessarily you removed it, changing it might have caused it as well (sorry, I don't understand what you meant with changing it to the alt version). The error is thrown in line 26 of class_adoptable.php which has this:
PHP Code:
$whereClause = (is_numeric($adoptinfo))?"id ='{$adoptinfo}'":"type ='{$adoptinfo}'";
$row = $mysidia->db->select("adoptables", array(), $whereClause)->fetchObject();
[B]
if(!is_object($row)) throw new AdoptNotfoundException("Adoptable {$adoptinfo} does not exist...");[/B]
It's when it recieves an ID and tries to fetch an object from the database.
Can you go to your database, table adoptables, and check what's up with the adoptable with an aid of 9?