It's possible that:
* The title is misremembered. You might be thinking of a different book by Mjoberg or another author with a similar title.
* The publication date is incorrect. Mjoberg wrote extensively about his travels and adventures, and it's possible the book you're thinking of was published later than 1912.
* The book is not widely known. Mjoberg's writings might not be easily accessible or may not be translated into English.
To help you find the book, it would be helpful to know:
* What is the book about? Is it about a specific animal, adventure, or region?
* Do you have any other details about the book? Is there a specific publisher or language?
With more information, I can help you find the book or determine if it exists.