There is nothing . . . improbable that for certain purposes an abbreviated version of the Gospel might be desired; but only a lunatic would leave out Matthew’s account of the Infancy, the Sermon on the Mount, and practically all the parables. (Canon Streeter, The Four Gospels, p. 158, cited in Dungan . . .)
David Laird Dungan cited the above passage from Canon Streeter’s The Four Gospels, p. 158, in his chapter in Jesus and Man’s Hope.
Dungan does proceed to offer evidence from the second century Patristic writings that someone really might have written an abbreviated Gospel that removed all the birth narrative and a very large portion of the teachings of Jesus. He quotes Irenaeus:
[Marcion] mutilates the Gospel which is according to Luke, removing all that is written respecting the generation of the Lord, and setting aside a great deal of the teaching of the Lord . . . (Against Heresies, 1:27:2)
And from the fourth century, Epiphanius:
For indeed [Marcion’s] Gospel appears to resemble Luke, but having neither beginning, middle, nor end [!], giving the appearance of a garment gnawed by many moths (Pan. adv. Haer. 42.11 — Dungan’s quotation, with his emphasis)