It's possible that:
* The name is misspelled. Check for variations in spelling, like "Lillian" or "Lillianna."
* The author uses a different pen name.
* The author is a self-published author. Self-published authors might not be listed in traditional databases.
If you have more information about the author or their work, such as the genre, specific titles, or a publishing house, it might be easier to find information about them.