@The General this is what I sent when the item has been added to the database and IF the inventory has been initialized, to the inventory (the inventory won't be initialized at login, but at the point (s)he opens the inventory).
PHP Code:
response = new ServerMessage(67);
product.Serialize(response);
session.sendMessage(response);
response = new ServerMessage(101);
session.sendMessage(response);
The first response is the notification you purchased X (what you see in the upper right corner) which has the exact same structure as products in the catalogue. The second is of course the inventory update. Try find a packet that accepts nothing more than the catalogue product constructor. If it still doesn't show up, Habbo removed it.