Well, let’s look at a couple of items of interest from the Catholic Church.
The belief in the corporeal assumption of Mary is founded on the apocryphal treatise De Obitu S. Dominae, bearing the name of St. John, which belongs however to the fourth or fifth century. [http://www.newadvent.org/cathen/02006b.htm]
So even the Catholic Church admits that the belief for the assumption of Mary comes from a dubious work. That should give a great feeling of assurance in what that organization believes and even proclaims to be something that must be believed.
Then we have this from the Catholic Church.
St. Juvenal, Bishop of Jerusalem, at the Council of Chalcedon (451), made known to the Emperor Marcian and Pulcheria, who wished to possess the body of the Mother of God, that Mary died in the presence of all the Apostles, but that her tomb, when opened, upon the request of St. Thomas, was found empty; wherefrom the Apostles concluded that the body was taken up to heaven.[ http://www.newadvent.org/cathen/02006b.htm]
So the RCC claims that all the Apostles were present at her death but not one of them wrote about it even though it is so central to beliefs of the RCC. We are to believe that the Apostles “concluded” that her body was taken to heaven but not one of them thought such an important event should be recorded.
How gullible must one be to fall for such a cult? And then have the audacity to proclaim as heretics those who hold to scripture only as the source for all truth.
James 2:24
The fathers comment on 2 Thessalonians 2:4
A verse I know that you reject.
{2:14} And so, brothers, stand firm, and hold to the traditions that you have learned, whether by word or by our epistle.
And so, brothers, stand firm AMBROSIASTER In order for God’s foreknoledge to remain favorable to their salvation, Paul warns them to stand and to presevere in the traditon of the Gospel. They must take care not to grow weary through idleness or sloth and so fail to complete the work of God which they have begun. and hold to the traditions that you have learned, whether by word or by our epistle AQUINAS The Apostles, led by the inward instinct of the Holy Spirit, handed down to the churches certain instructions which they did not put in writing, but which have been ordained, in accordance with the observance of the Church as practiced by the faithful as time went on. ATHAN The very tradition, teaching, and faith of the Catholic Church from the beginning was preached by the Apostles and preserved by the Fathers. GREG That is, by succession from the Apostles through the saints who came after them. EPIPHAN We must turn to tradition, for everything cannot be received from the divine Scriptures. That is why the holy Apostles handed down certain things in writings but others by traditions. IRENAEUS In this order, and by this succession, the ecclesiastical tradition from the apostles, and the preaching of the truth, have come down to us. And this way there is one and the same vivifying faith, which has been preserved in the Church from the Apostles until now, and handed in truth. VINCENT Here perhaps, someone may ask: Since the canon of the Scripture is complete and more than sufficient in itself, why is it necessary to add to it the authority of ecclesiastical interpretation? As a matter of fact, Holy Scripture, because of its depth, is not universally accepted in one and the same sense. The same text is interpreted different by different people, so that one may almost gain the impression that it can yield as many different meanings as there are men. Thus, because of the great distortions caused by various errors, it is, indeed, necessary that the trend of the interpretation of the prophetic and apostolic writings be directed in accordance with the rule of the ecclesiastical and Catholic meaning.
You theorize that the Apostles made a habit of writing down everything that happened of spiritual significance? St. John stated quite plainly that they did not write everything down.
However, the report was certainly passed along verbally and perhaps through written documents since lost. Relics of all the Apostles and martyrs were greatly sought after by early Christians for miraculous healing power and Mary's relics would have been the most highly prized of all. The unavailability of Mary's relics or records of her relics is solid evidence that her body was never buried according to the standard practice. Given that, the most likely scenario (and the historically chronicled report) was her bodily assumption into heaven. At least it is the most likely scenario for any Christian who accepts the reality of miracles.