And you have proof of this? Proving a negative is hard.
Q was postulated because of the similarities, often word-for-word, between Matthew and Luke. The simplest explanation for such similarities is that another document existed that both used.
From
The Authors of the Gospels:
There is not the slightest historical evidence, or even a hint, that
Q or its author ever existed. If
Q had existed, it would have been the most precious scroll of Christianity during the first 50-70 years of the new religion. According to the Markans we owe the preservation of
The Our Father and
The Beatitudes to
Q. Mark did not bother to record them. If
Q had been the key document containing the sayings of Christ, it would have been treasured, copied and passed from hand to hand and read at Services.
Markan priorists want us to believe that the community that produced
Q later lost it, although it was so important that Matthew and Luke, unknown to each other, made much use of it. Then the communities of Matthew and Luke also lost it. It is hard to believe that only two copies were made of
Q and these just happened to be in the possession of the isolated communities in which Matthew and Luke lived and these communities lost them. If more copies were made for many communities, Markans have to explain how all these copies of this key Christian document were lost. Also, how did ‘Q’ disappear without leaving even a vague reference or echo in any piece of Christian or heretical literature?
Those who hold the Markan theory demand the most stringent proof for the historicity of the Gospels, for which we have much historical evidence. Yet they accept conjectures and theories about
Q, based on further conjectures and theories for which there is no evidence at all. In reality
Q was created in the 19th century, out of nothing, to fill a hole in the Markan priority theory.