If Muhammad was illiterate, who then wrote the Qur'an for him, and where is he now?

The Prophet heard the verses of the Quran in revelation, then recited it to his companions who memorized it. Some of his companions could read and write and they wrote down the verses on scraps of leather, bone or whatever was to hand. Later, when the Quran's revelation was complete, all the verses were collected into one volume.