Short answer:  No.

One is not a member of the Church until baptism.  Even those who accept "Baptism of Blood" and "Baptism of Desire" must necessarily agree that such an extraordinary means of justification must make one a member of the Church only at the time of death and not before.

I remember reading a short biography of Paul VI a few years ago.  I wish I could remember who the author was and where I read it, suffice it to say that it was not Traditio or the Dimond Brothers.  At the time, the author was considered to be credible on Church matters though I can't say if he really was or would be considered to be now since I don't remember who he was.

The biography claimed that there was no record in the parish archive's of Giovanni Montini's baptism in the village of Concesio, where he was born.  The author did note that many such archives had been destroyed one way or another during the two World Wars that ravaged Europe since his baptism though the author did find it curious that some other contemporaneous records he was researching had not evidently vanished as well.  However, he did not jump to the conclusion that Montini was never baptized, only that there were some irregularities regarding his life.

I've always been curious that this issue was never pursued.  If evidence can be unearthed that he was never baptized that would surely end all questions regarding the validity of the Vatican Council II and all his works!  But, perhaps, it was merely an oversight of this one author.

TKGS,

  The story on Paul VI's baptismal record not being able to be located can be found in Dr Rama Coomaraswamy's "The Destruction of the Christian Tradition."  
  I had the same thoughts as you, it would make it even easier to show that Vatican II could not come from the Church.

TKGS,

  The story on Paul VI's baptismal record not being able to be located can be found in Dr Rama Coomaraswamy's "The Destruction of the Christian Tradition."  
  I had the same thoughts as you, it would make it even easier to show that Vatican II could not come from the Church.

Thanks.  I don't believe I've ever read anything by Coomaraswamy, though I have heard of him.  Perhaps what I had read used this as his source.  I really don't know.  I am glad, though, that someone has finally shown a source on this.  I've spoken of it before but no one I've known has ever heard this which had led me to wonder (if just a little) if my memory about this was faulty.