We all know and can appreciate that the Qur'an can never be altered in anyway shape or form, but us humans can only get access to a copy of the Qur'an, i.e. the Mus'haf. Can we be sure that the Mus'haf is also perfectly intact and unaltered?
From the life of Prophet (pbuh) we know that original means of protecting the Qur'an is through memorization. Today, it is estimated that there are more than 10 million huffaz (person who memorized the Qur'an)* Therefore, for a mass printed mushaf, if there are intentional or accidental errors, it won't take long before someone notices it and warn people. Incidents like The True Furqan might happen in future, but personally, I don't think it has any chance to fool anyone. If you are in doubt about a certain copy of mushaf, you can visit a local huffaz to get it examined, or compare it to a trusted copy to be sure if it's intact.