"The most probable scenario is that Matthew was there, an eyewitness who made shorthand notes of what Jesus said."
Most probable scenario is that this scenario is another theory. Be careful of Thiede and of others who announces his or her discoveries to the media around Christmas and Easter.
http://www.askwhy.co.uk/truth/210Thiede.html#Gasping%20in%20Astonishment"We agree with Thiede when he wrote �Caution is always the best approach in the dating of manuscripts�. [97] In this article an attempt has been made both to hear and to critically investigate his claims regarding the date of P. Magd. Gr. 17 = P64. Although we recognise the service that he has performed in facilitating a reexamination of methodological presuppositions, our verdict on his claims is a negative one. The very early manuscripts to which Thiede appealed for close parallels to P64 turned out to be not as close as the somewhat later ones which he had overlooked. Although there is no absolutely definite evidence by which P. Magd. Gr. 17 = P 64 can be dated with certainty, the available evidence points to a date around AD 200. To be on the safe side I would suggest plus or minus fifty years as the possible range."
http://www.tyndale.cam.ac.uk/Tyndale/staff/Head/P64TB.htm1) The main conclusion, in relation to Thiede's article, is that a first-century dating is definitively ruled out by the association of the hand of P64 with the biblical majuscule style.
2) Roberts' first edition and revised edition were evidently hurried and left room for improvements (palaeographical, codicological, text-critical).
3) Thiede shows up some (not all) of the faults in the earlier
editions, but also continues or introduces some errors.
4) In relation to the question of dating, Thiede makes two main
errors of method:
(i) He makes comparisons based on individual letter forms, without
assessing the overall style of the hands in which the letters occur.
(ii) He does not draw relevant evidence into consideration, in
particular:
(a) the association of the hand of P64 with the biblical majuscule
style;
(b) the evidence of P4.
http://www.ibiblio.org/bgreek/test-archives/html4/1995-09/10441.htmlHis redating on paleographical grounds is seriously flawed in four ways.
First, he does not indicate how four great paleographers could all concur on a lowered redating of the Matthew fragments to a date ca. 200 and still be in error.
Second, he compares letters in these fragments from Egypt [Luxor is purchase place, hand compares with {P}4, from Philo codex binding] with material from Herculaneum in Italy (that may be from ca. 40 b.c.e. on provenance grounds, with a terminus ad quem of 79 c.e.) and from Qumran in The Land, and from elsewhere in the wilderness of the Dead Sea (NaHal Hever).
Third, he compares individual letters without an appreciation of the characteristics of their formation or the hands of which they are a part. Fourth, his assembly of mss for comparisons is not a coherent set, and was apparently chosen primarily as a group of mss which *could* be dated in the first century c.e., regardless of their other features. Thiede did not recognize that a two-column codex such as {P} 64 --Magdalen Gr. 17 -- has no similarly-constructed examples with which to be compared. He does not recognize the need to provide some explanation for the appearance of a two-column codex at least a century earlier than all other examples of two-column codices. See Turner, op. cit.
Finally, Thiede (1995) and Roberts (1953) both transcribed the fragments as thought they contained <i>nomina sacra</>, and as though the use of <i>nomina sacra</> was not restricted to <gr>KURIOS, KURIE</>, or <gr>QEOS, QEOU</>, but rather extended to abbreviations of <gr>IHSOUS</>.However, and I must state this emphatically, there is no visible support" http://ccat.sas.upenn.edu/~petersig/thiede.txt.final.reply