Authors prior to Marcion do not refer to any Gospel ‘as a sequence of events or a “story”. Nowhere are fixed credal formulations called “Gospel”’. What the famous New Testament scholar Helmut Koester summarized in rather dry words, kept Kurt Aland awake during the night.
The fact is clouded by the boundaries between the disciplines of New Testament Studies and Patristics. The well-known reference work, Biblia Patristica, for example, covers texts ‘from the origins to Clement of Alexandria and Tertullian’ in its first volume, but excludes all writings that can be found in the New Testament. If these were included, it would become even more apparent that pp. 223-415 of this volume listing over 10,000 quotes (!) from Matthew, Mark, Luke and John for the period from Marcion onwards, does not provide a single one (!) for the time before Marcion, and would we add the canonical literature - the same would still be true, with one massive exception: The Synoptics copied each other partly literally. The first arguable cases of authors who begin to quote the Gospels are those who are sometimes dated to the beginning of the second century (Ignatius, Papias, Hegesippus), which, however, many scholars rather date contemporary or later than Marcion. How can we account for this discrepancy in the reception of the Gospels, if these later canonical Gospels were written before 100, or around 70, or, as some opt for, in the early 40th?
I'd give a lot for somebody who can come up with a convincing answer.