P0SSIBLY L0ST AT SEA IN NEW ZEALAND AREA. Mike Cisarik, once one of Southern California's most prominent civil rights lawyers, quit his practice about five years ago and headed to the South Seas by himself in a 40-foot yacht called The Rebel. He said he wanted to leave the rat race behind. The mystery is whether he intended to disappear. He has not been heard from since the first week of June, a few days after he left New Zealand, sailing north for the Tonga Islands. Ordinarily, that 1, 000-mile journey takes about two weeks. But, according to authorities in New Zealand, Cisarik carried enough food, water and fuel to last six months--or more. Marine authorities said Wednesday they have no reason to believe that Cisarik has met his death, but they stressed that they have ruled nothing out--including the possibility that he fell overboard and drowned.