It's not impossible that "Treasure Island" may have been at the back of Herge's head when he worked on "Unicorn" and "Red Rackham's Treasure" but there are sources that suggest that his actual book reading was limited. He may have read it or else he knew of it.
I don't think there's any doubt that he knew it. Haddock says on page 25 "Red Rackham is dead! With a yo ho ho, and bottle of rum!" which is pretty much a direct quote (the yo ho ho bit) from the song "Fifteen Men on a Dead Man's Chest", which was written by Stevenson for Treasure Island
What's more, the whole theme of the book, the pirates, treasure maps, etc. Treasure Island is the
iconic pirate story, and its influence is massive. It was definitely an influence, without a doubt.
In my copy, the title is in French
[In reference to which language Tintin reads Treasure Island in Castafiore Emerald]
Thanks cigee! Probably just a mis-pressing in mine then. But I like it!Edit
Note to mct16: I'm dreadfully sorry, I seem to have inadvertently deleted your post that came prior to this one, which was in reply to Balthazar. A slip of the finger I'm afraid, my apologies! If you wouldn't mind making it again it would get me out of trouble.