you need to get rock-solid information about what it is you need before you take any trips to any embassies
If he only needs to go back to Poland (from where he can re-apply for his passport and visa) - he only needs temporary travel document as Zman mentioned. This is only valid for travel back to Poland, as no other country will allow him in on this document. Once within Shengen he can travel on "Dowod Osobisty".
He may need to show proof of reporting the stolen passport to the Police in order to obtain the clearance letter to travel - I don't think he needs to cry :)