jno, that the lives of most ordinary people are lost to us does not explain the complete blankness surrounding Jesus. I have already mentioned supposed contemporaries of his of which we know a lot. Julius Caesar preceded Jesus' time by a century or so but there is a wealth of information about him and his contemporaries.
Yet a man who is supposed to have had a miraculous birth, who practised miracle cures and performed other miraculous things, who counselled wise men, who preached to thousands at a time, who raised people from the dead, who caused the Sanhedrin and Pilate to behave completely out of character and who rose from the dead himself goes unrecorded just by chance? Can you really believe that? Yes, I suppose you must.
But that is beside the point. You still have not offered an explanation as to how that knowledge about Mary's body, which only she would have been privy to, remained a secret for nearly a century and then emerged ever so casually with no evidence to support it.
You don't have to explain it, of course, but those of us who look on these things with more intellectual rigour are naturally curious as to why people believe such amazing things on such a flimsy basis. Faith, I suppose: a euphemism for blind credulity.