Why is it that Neither Eutychius Nor Severus Mention the Translatio of the Relics of St. Mark?

I think the two Egyptian churches were utterly embarrassed by the incident and wanted to bury any mention of the dishonor. It is interesting though that already in Severus, over a century after the theft, an effort is made retell the history of the history of the period WITHOUT referencing the body of St. Mark. Severus' NEW history reads:

And in the year 360 of Diocletian (646 CE), in the month of December, three years after Amr had taken possession of Memphis, the Muslims captured the city of Alexandria, and destroyed its walls, and burnt many churches with fire. And they burnt the church of Saint Mark, which was built by the sea, where his body was laid; and this was the place to which the father and patriarch, Peter the Martyr, went before his martyrdom, and blessed Saint Mark, and committed to him his reasonable flock, as he had received it. So they burnt this place and the monasteries around it.

And at the burning of the said church a miracle took place which the Lord performed; and that was that one of the captains of the ships, namely the captain of the ship of the duke Sanutius, climbed over the wall and descended into the church, and came to the shrine, where he found that the coverings had been taken, for the plunderers thought that there was money in the chest. But when they found nothing there, they took away the covering from the body of the holy Saint Mark, but his bones were left in their place. So the captain of the ship put his hand into the shrine, and there he found the head of the holy Mark, which he took. Then he returned to his ship secretly, and told no one of it, and hid the head in the hold, among his baggage.

It is hard to imagine that even if a fire of this kind was to have consumed the church that temperatures could have reached sufficient temperatures to cremate bones. The standard funeral home cremates bodies at 1400 degrees Fahrenheit. Under more "normal" conditions (as in the sorts of fires that occur by accident rather than design) bones will burn to some extent, but will rarely be completely consumed.

It should be obvious then that Severus is 'covering up' the translatio of the relics of St. Mark by arguing essentially that the corpse 'disappeared' in the Muslim conquest of Egypt. This is ridiculous and part of the Coptic development of a 'replacement' of the original significance of the body by just the head (which continued to be the center of Coptic worship.