the well-known 'missing page' 102 (or 100, depending on the edition you have)
I'm not sure which versions you are referring to here, but it doesn't actually appear as those pages in the copies I have to hand - in the first English facsimile, for example, it is included as page 97a; in the 1973 Archives Hergé
it appears as page 140.
Sticking with 97a seems to be the best bet, as it therefore doesn't affect the order pages in editions in which it does or doesn't appear.
The whole numbering of the book is a minefield, as the facsimile editions place no page number on the first left-hand page, and put "1" on the right-hand page.
The "standard edition" which came out from Methuen makes the "first" page page 4, which was unusual in UK books, as it counts from the front cover (this has actually become more common in recent years, thanks to computer publishing software often defaulting to the cover being treated as page 1, whereas in the past the cover wasn't included in the numbering scheme).
The new standard French colour edition doesn't number the first (left-hand) page, and puts page 1 on the first right-hand page, in the manner of the facsimile, even though it would be (including the cover) page 11 in a strictly numerical sequence.
Obviously, this was a mistake.
Can we be certain of that? It's not difficult to overlook the jump, given the fact that the story isn't the most straight forward tale to begin with; the standard Methuen edition I have doesn't include it, and I can't say I'm aware of complaints that it's difficult to follow because Tintin gets a bloody nose (I mean, he loses a black eye early in the story between standing outside a tailor's shop, and going into the shop and being served - is that any more confusing?).
I really believe that Hergé wanted this original page to be included in the story.
It is absolutely fine for you to believe this, but I would need proof. He was responsible for getting the plates prepared, so he may have been aware from the outset. It was damage to the printing plates, and Hergé being unable to afford new ones which was one of the reasons that the book went out of print to begin with; perhaps the loss of a page made sense financially to him, if it reduced his overhead.
why did Casterman leave the 'missing page' out of the new release?
Well, if Hergé was the one disinclined to include it, and had authorized the removal in the original edition, then perhaps they didn't see it as appropriate to do so?
The page has
been coloured, and was included as a bonus print in the deluxe numbered edition, which also featured an alternate colour cover design, so perhaps at some time it will be re-included.