edit: btw, this is a sp. z o.o. (a Polish equivalent of LLC) with a minimum capital required by law, so you you will only be able to recover 5000 zł from them (that's about ~1650 USD at current exchange rates). If you want to recover more than that, then you will need to go after MT.GOX CO.LTD.
According to this
http://prawo.rp.pl/artykul/597246.html, he can get more than 5000PLN from the shareholders.
That's what I said: MT.GOX CO.LTD is the sole shareholder.