The question regarding Japanese intentions in the event that the Pacific Fleet was absent from Pearl Harbor is a fascinating one. Absence (from both Pearl Harbor and Lāhainā) was the true nightmare scenario for the Japanese.
Along with the team of co-authors Sam Tagaya, Bob Cressman, and John Di Virgilio, I am in the midst of writing portions of the fifth volume of our "Pearl Harbor Tactical Studies" series for Naval Institute Press. This fifth volume will deal with the Japanese story over Pearl Harbor proper, and will address Japanese intentions pertaining to absence of the fleet. Not wishing to be too evasive here, know that we are trying to safeguard sources, analysis, and conclusions.
However, it is safe to say the following. Although the Japanese intended to attack airfields on O'ahu in such circumstances, there also were to be thorough searches for the American fleet conducted by Kidō Butai's air groups. There are also surviving detailed contingency plans that set forth actions to be taken if units of the Pacific Fleet lay at the Lāhainā road-stead. We will be going into this in quite some detail as well.
Additionally, there has been speculation for decades regarding what was actually planned for follow-up raids against Pearl Harbor, and the supposed debate on Akagi's bridge among Fuchida, Nagumo, and the latter's staff. Rest assured that we will go into great detail regarding this issue.
Hate to leave you hanging, but... wait for the book!