Hi Momber, and welcome to the forum!
The first page of
One Night in Shanghai is reproduced in
The Art of Hergé, Volume 2, by Phillipe Goddin, translated by Michael Farr (
here's an Amazon link to it, if you're not familiar with it).
According to the book's caption text, this first page was the only page ever produced.
The book also shows single panels from two other one-page demos of different adventure strip ideas produced by Hergé and Jacobs, under their joint post-war pseudonym, Olav.
I think the pages were shown to a few publishers, but weren't taken on. And shortly afterwards, Hergé and Jacobs were given permission to work again, under their own names, thanks to the intervention of Raymond Le Blanc and his
Tintin magazine idea.
The single page of
One Night in Shanghai borrows many elements of
The Blue Lotus, but is drawn in a more American "noir" style, a bit like Jacobs' most loose and sketchy style.
By the way, I believe the
Art of Hergé series is basically a translated and abridged version of Phillipe Goddin's more extensive muti-volume
Chronologie series, so presumably this page also apears in the relevant volume of that.