It's possible:
* The name is misspelled: Perhaps you're thinking of a different name, similar to Stephen Frederick Tillman. Double-check the spelling and try searching again.
* The author is less known: There might be an author with that name who has written books, but they might not be widely published or popular. It's worth searching online using specific keywords like "Stephen Frederick Tillman author" or "Stephen Frederick Tillman books" to see if any results come up.
* The author uses a pen name: It's possible the author writes under a different name. You might be able to find information about them under another pseudonym.
To help me assist you further, could you provide any additional information you might have about the author, such as:
* The genre of books they write: Is it fiction, non-fiction, poetry, etc.?
* Any specific titles you might remember: Do you recall the name of any of their books?
* Any other details about the author: Do you know anything about their background or where they are from?
With more information, I might be able to help you find the author you're looking for.