How Incomplete is Our Knowledge of 1st-Century Rome?
This question is motivated by the declaration by Maeglin in the GD "BC/AD vs. BCE/CE" thread that he is a professional Roman historian. It is something that I have long wanted to ask an expert.
There are at least two major events in the birth narratives of Jesus that seem significant enough to have been reported by secular historians, but were not (to our knowledge).
The most obvious is the worldwide census of Luke, chapter 2. He claims that in the year Jesus was born, Augustus Caesar decreed that a census of all the world be taken, and that people had to travel to their ancestral homes for the purpose.
Even assuming he meant only the Roman Empire, there are many problems with this passage. Given the extent of the Empire, travel to ancestral homes, say for a legionnaire stationed in Spain whose ancestors were from Syria, might take over a year for the round trip, and it makes little sense that a man whose land, cattle, and slaves are located in one place should go somewhere else to have them assessed. Luke also names Quirinius as the governor of Syria during the census, which is about ten years too late for Jesus to have been born during the reign of Herod the Great. There is evidently no record of this census outside of Luke.
In Matthew 2, Herod is alleged to have perpetrated the Slaughter of the Innocents, in which every male child under two years old who lived in "Bethlehem and its environs" was murdered. Again, there is no record of this outside of Matthew.
It seems impossible to me that there could be no surviving records of an Empire-wide census. Covering up a local massacre seems more plausible, but since Herod ruled at Roman sufferance, it seems likely to me that someone would have complained to Rome, and that Herod's enemies, at least, would have made it notorious.
But neither incident appears in secular history, or even the other Gospels. Apologists claim that "absence of evidence is not evidence of absence," because our records from 2000 years ago are not complete.
To avoid getting this moved to GD, I acknowledge that some people claim that the stories are not intended to be historical. If anyone believes that they are allegorical, or that they are intended to tell a "higher truth" than mere facts, that's fine, but that's not my question.
My question is strictly historical, and intended for experts on first-century Roman or Jewish history: Is it plausible that accounts of these incidents, if they occurred as described, would be lost to us?