Far too late to do you any good, but the Busena Terrace is still alive and well.

http://www.terrace.co.jp/en/busena/

Apparently, the English site still doesn't accept online reservations, but does list a phone number to call direct.

http://www.terrace.co.jp/en/busena/g...s/roomrate.php

Shouldn't be too hard to fumble your way through the Japanese reservations page to see what rooms are open though.

http://www.terrace.co.jp/reserve/ind...edium=go2plans

I will say that the actual resort is much nicer and user friendly than the English website.