I should know better, but I'll say something here.
In the 1st century, written evidence was less important than oral evidence. Think about it--back then, most people couldn't read, and even if you could read, you had no way to verify the real author of a document. A real person, whose identity could be verified, standing in front of you and speaking, was far more trustworthy than a piece of papyrus. As long as Jesus' original followers were around to tell the story, they didn't need a document to describe what happened.
In any case, the Gospel of Thomas was not suppressed by "the church." There has never been any time in the history of Christianity when the whole Christian church was unified under a single authority. Since there was no "church authority," there was no one to suppress books from the Bible.
Shafto: while the New Testament tends to gloss over the political side of Jesus' movement, it's clear that he was seen as a dangerous rebel. "Christ" is a political title as well as a religious one. And the description of crowds welcoming Jesus into the Jerusalem indicates a threat in Jesus' movement. And the Book of Revelation looks forward to and celebrates the future destruction of the Roman Empire.
Back to the original question...I think that this is a strong argument, but I'm not out to disprove it. :) It's worth noting also that the disciples were totally shocked both by Jesus' death and by his resurrection, and that it took time for them to agree on what happened.
It's clear that something happened that day...one of the most interesting pieces of evidence is Matthew 28:11-15 (http://bible.oremus.org/?ql=133672567). That passage is designed to disprove the unbeliever's claim that the disciples stole Jesus' body. If Christians and non-Christians were arguing about *how* Jesus' body vanished from the tomb, they must have agreed *that* Jesus' body vanished from the tomb.