You're right that this book doesn't exist. It's one of a series of three or four covers for non-existent Tintin books by an artist called Harry Edwood. His work has only been published on-line (but even so, breaks the copyright laws, of course, so you did absolutely the right thing by not giving any link or info as to where you found the image - something that could provoke Moulinsart into closing down this this forum!)
Harry Edwood's easily the best Tintin pasticher I've seen - the only one who's drawing standard and style comes close to that of HergÃ© and his team, though his storytelling/scripting in the few narrative strips he's done aren't really up to HergÃ©'s standard. (I can completely see why HergÃ©'s estate have rigourously obeyed HergÃ©'s instructions for there to be no new Tintin stories after his death.)
To save repeating info that is already on this site, here's an old thread on the subject of Harry Edwood's work:https://www.tintinologist.org/forums/index.php?action=vthread&forum=11& topic=210
You'll notice that one French contributer to the thread asserts that Edwood has in fact been working on a full comic version of Le Rocher Des Kangourous. But even if that's true, given the legal position, I doubt we'll get to see it until Tintin comes out of copyright in 2053!