Muslims accept the original unaltered Torah (as revealed to Moses) and the original unaltered Bible (as revealed to Jesus) since they were revealed by God. But none of these scriptures exist today in their original form or in their entirety. Therefore, Muslims follow the subsequent, final and preserved revelation of God, the Qur'an.
If all Qur'ans in the world today were destroyed, the original Arabic would still remain. This is because millions of Muslims, called "hafiz" (or "guardians") have memorized the text letter for letter from beginning to end, every word and every syllable. Also, chapters from the Qur'an are precisely recited from memory in each of the five formal prayers performed daily by hundreds of millions of Muslims throughout the world.