How the Existence of Quranists Refutes Them

How the Existence of Quranists Refutes Them Ahmad, Abu Dawood and al-Haakim reported with a saheeh isnaad from al-Miqdaam that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: "Soon there will be a time when a man will be reclining on his couch, narrating a hadeeth from me, and he will say, 'Between us and you is the Book of Allaah: what it says is halaal, we take as halaal, and what it says is haraam, we take as haraam.' But listen! Whatever the Messenger of Allaah forbids is like what Allaah forbids." Source: Al-Fath al-Kabeer, 3/438. Al-Tirmidhi reported it with different wording, and said that it is hasan saheeh. Sunan al-Tirmidhi bi Sharh Ibn al-'Arabi, al-Saawi edn., 10/132 The Hadith makes a prophecy that in the future people who reject Hadith will come. Since no one during the Salaf ever rejected all Hadith, how did the compilers of this particular Hadith know that Quranists will come in the future? Ironically the very existence of Hadith Rejectots proves the Hadith to be true