Was Matthew 28:19 in the original writing of the gospel of Matthew?

Some manuscripts have Matthew 28:19 missing.

The didache affirms Matthew 28:19
"7:1 But concerning baptism, thus shall ye baptize.
7:2 Having first recited all these things, baptize {in the name of the Father and of the Son and of the Holy Spirit} in living (running) water.
7:3 But if thou hast not living water, then baptize in other water;
7:4 and if thou art not able in cold, then in warm.
7:5 But if thou hast neither, then pour water on the head thrice in the name of the Father and of the Son and of the Holy Spirit.
7:6 But before the baptism let him that baptizeth and him that is baptized fast, and any others also who are able;
7:7 and thou shalt order him that is baptized to fast a day or two before."
http://www.earlychristianwritings.com/text/didache-lightfoot.html

Several church fathers quoted Matthew 28:19.

ON BAPTISM For there has been imposed a law of baptizing, and its form prescribed: Go, [Jesus] says, teach the nations, baptizing them in the Name of the Father and the Son and the Holy Ghost. Tertullian wrote that quote before his death c. 225. That's a century before Nicea.

Ignatius of Antioch (ca. AD. 107-112)

    Chapter IX.-The Old Testament is Good: the New Testament is Better.

    … The priests indeed, and the ministers of the word, are good; but the High Priest is better, to whom the holy of holies has been committed, and who alone has been entrusted with the secrets of God. The ministering powers of God are good. The Comforter is holy, and the Word is holy, the Son of the Father, by whom He made all things, and exercises a providence over them all. This is the Way which leads to the Father, the Rock, the Defence, the Key, the Shepherd, the Sacrifice, the Door of knowledge, through which have entered Abraham, and Isaac, and Jacob, Moses and all the company of the prophets, and these pillars of the world, the apostles, and the spouse of Christ, on whose account He poured out His own blood, as her marriage portion, that He might redeem her. All these things tend towards the unity of the one and only true God. But the Gospel possesses something transcendent [above the former dispensation], viz. the appearing of our Saviour Jesus Christ, His passion, and the resurrection itself. For those things which the prophets announced, saying, "Until He come for whom it is reserved, and He shall be the expectation of the Gentiles," have been fulfilled in the Gospel, [our Lord saying,] "Go ye and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost." All then are good together, the law, the prophets, the apostles, the whole company [of others] that have believed through them: only if we love one another.
http://ccel.org/fathers2/ANF-01/anf01-20.htm#P2080_351579

Chapter II.-Unity of the Three Divine Persons.

There is then one God and Father, and not two or three; One who is; and there is no other besides Him, the only true [God]. For "the Lord thy God," saith [the Scripture], "is one Lord." And again, "Hath not one God created us? Have we not all one Father? And there is also one Son, God the Word. For "the only-begotten Son," saith [the Scripture], "who is in the bosom of the Father." And again, "One Lord Jesus Christ." And in another place, "What is His name, or what His Son's name, that we may know? " And there is also one Paraclete. For "there is also," saith [the Scripture], "one Spirit," since "we have been called in one hope of our calling." And again, "We have drunk of one Spirit," with what follows. And it is manifest that all these gifts [possessed by believers] "worketh one and the self-same Spirit." There are not then either three Fathers, or three Sons, or three Paracletes, but one Father, and one Son, and one Paraclete. Wherefore also the Lord, when He sent forth the apostles to make disciples of all nations, commanded them to "baptize in the name of the Father, and of the Son, and of the Holy Ghost," not unto one [person] having three names, nor into three [persons] who became incarnate, but into three possessed of equal honour. (Epistle of Ignatius to the Philippians;
http://ccel.org/fathers2/ANF-01/anf01-31.htm#P2862_463028

Irenaeus (ca. 130-200)

    Chapter XVII.-The Apostles Teach that It Was Neither Christ Nor the Saviour, But the Holy Spirit, Who Did Descend Upon Jesus. The Reason for This Descent.

    It certainly was in the power of the apostles to declare that Christ descended upon Jesus, or that the so-called superior Saviour [came down] upon the dispensational one, or he who is from the invisible places upon him from the Demiurge; but they neither knew nor said anything of the kind: for, had they known it, they would have also certainly stated it. But what really was the case, that did they record, [namely,] that the Spirit of God as a dove descended upon Him; this Spirit, of whom it was declared by Isaiah, "And the Spirit of God shall rest upon Him," as I have already said. And again: "The Spirit of the Lord is upon Me, because He hath anointed Me." That is the Spirit of whom the Lord declares, "For it is not ye that speak, but the Spirit of your Father which speaketh in you." And again, giving to the disciples the power of regeneration into God, He said to them, "Go and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost." For [God] promised, that in the last times He would pour Him [the Spirit] upon [His] servants and handmaids, that they might prophesy; wherefore He did also descend upon the Son of God, made the Son of man, becoming accustomed in fellowship with Him to dwell in the human race, to rest with human beings, and to dwell in the workmanship of God, working the will of the Father in them, and renewing them from their old habits into the newness of Christ. (Irenaeus Against Heresies Book III;
http://ccel.org/fathers2/ANF-01/anf01-60.htm#P7716_2104969

Tertullian (ca. 160-220)

    Chapter XX.-Christ First Delivered the Faith. The Apostles Spread It; They Founded Churches as the Depositories Thereof. That Faith, Therefore, is Apostolic, Which Descended from the Apostles, Through Apostolic Churches.

    … Accordingly, after one of these had been struck off, He commanded the eleven others, on His departure to the Father, to "go and teach all nations, who were to be baptized into the Father, and into the Son, and into the Holy Ghost." Immediately, therefore, so did the apostles, whom this designation indicates as "the sent." … (Tertullian The Prescription Against Heretics;
http://ccel.org/fathers2/ANF-03/anf03-24.htm#P3389_1178816

Conclusion: Matthew 28:19 was in the original gospel of Matthew.