It's true dave. The Americans in Hawaii knew but kept it to themselves.
"Within minutes of the tsunami forming on Sunday, U.S. officials at the Pacific Tsunami Warning Center in Hawaii began tracking the waves. But the scientists claimed they had no one to contact in the Indian Ocean region about the possible danger. One exception was the British-owned island of Diego Garcia that houses a major US Naval base. The Independent of London reports that U.S. officials in Hawaii did warn Diego Garcia about the possible tsunami and the island suffered no major damage."
