I wonder why no attempts were made to rectify it when it was redrawn in 1955?
I think that the answer is sort of contained in your post - it's an adventure of wild coincidence, and fantastical incidents all the way through, so fixing one would simply bring another to the fore, which then would probably have become the focus of reader dissatisfaction.
Had Hergé indicated that Tintin knew of the gang being in India, one's mind might be left to concentrate on the fact that he had managed to cover an impossible distance in a 'plane ill-equipped to undertake such a voyage.
However, you're not alone in wondering about this, so your post has been moved to this existing thread.
As Mikael says above
, Hergé was improvising the story on a week-by-week basis, so it was just a means of continuing the story, rather than an actual attempt at plotting out a coherent adventure.
I'd also forgotten until I re-read it just now that I'd noted above
that the Nelvana adaptation made an effort to darn that particualr plot-hole, by deftly inserting the clues that Tintin needed in the information he discovered in Fouad's office, to link the gang to a location India.
Hats off to them for that, and it does seem like something that Hergé could have done, had it occurred to him!