BritinBritain
Per Ardua Ad Astra
I suspect there are a number of reasons for this:
1. The Japanese task force left for Pearl Harbour on the 26th November and the Enterprise left Pearl on the 28th November, Lexington left on the 5th December and Saratoga was in San Diego, the Japanese enforced strict radio silence during travel so they would not have been told they had left even if they knew and Enterprise was due back that day (and it's aircrews suffered casualties at Pearl Harbor so they were close).
I can understand why the Japanese fleet sailing for Pearly had radio silence, but I would assume the Japanese Navy HQ would have a recall code word.
I'm also surprised that with the sabre rattling of the Japanese there were not Allied submarines operating in the area of thew Japanese homelands.
Its also been suggested that the attack on Pearl Harbour was known by Allied leaders before the actual attack.