Islam critiqued asks; The Quran? much of it is gone!

In answer to the video "Muslims' Worst anti-Christian Polemics: Corruption of the New Testament"

This is a common hadith brought up by Islam's critics. Ibn Umar said

“Let none of you say ‘I have acquired/ahatta the whole of the Qur’an’. How does he know what all of it is when much of the Qur’an has disappeared/faatahu? Rather let him say ‘I have acquired what has survived/ma tayassara minhu.'” 

This is a blatant mistranslation. The Arabic speaks of knowledge/understanding

"Let no one say: I have encompassed/understood the whole of the Quran. How does he know what all of it is when much of the Quran escapes him? Rather, let him say: I have encompassed whatever amount of it has been facilitated (for me to grasp).”

ibn Umar, to whom the quote belongs, wasnt refering to the Quran's collection. He was from a conservative school of thought in matters of Quranic exegisis, even criticizing ibn Abbas' zeal in comenting the sacred text. That is why he warns against those assuming that they are capable of fully grasping this mighty, intricate and deep word of God.