def get_existing_item(self, item):
        """
        Lookup item in remote service based on keys.
        :param item: D4S2Item data contains keys we will use for lookup.
        :return: requests.Response containing the successful result
        """
        params = {
            'project_id': item.project_id,
            'from_user_id': item.from_user_id,
            'to_user_id': item.to_user_id,
        }
        resp = requests.get(self.make_url(item.destination), headers=self.json_headers, params=params)
        self.check_response(resp)
        return resp