That's normal for ancient writings -- we don't even have a signature of Julius Caesar in existence, does that mean he never existed.
ETA
And some of the Christian manuscripts we have are much sooner (by hundreds of years) closer to the time of events than most other ancient writings. From the source cited in post# 604.
"By contrast, the manuscripts for most other ancient books date from about a thousand years after their original composition. To compare this to the other ancient writings: Homer’s Iliad is in “second place” behind the New Testament with no more than 643 copies.
And of Plato’s Tetralogies only seven copies are known. Also the earliest copy of Plato’s work is dated about 1,200 years after he produced the original. The oldest copy of the Iliad dates about 500 years after the original. This is a dramatic contrast to the oldest papyrus text of the New Testament, a part of chapter 18 of the Gospel of John, dated at near 125 AD."
http://www.windmillministries.org/frames/CH11A.htm