* The name is misspelled. Perhaps there's a slight variation in the spelling.
* The author uses a pseudonym. It's not uncommon for authors to publish under different names.
* The author is relatively unknown or unpublished. There are many talented writers who haven't achieved widespread recognition.
To help me find information, could you please provide more context:
* What kind of books do you think Gilbert Spearman might have written? (Genre, subject, etc.)
* Do you have any other information about the author, like their nationality or a specific book title?
With more details, I might be able to help you track down the author.