After disappearing three months ago Coast Guard Petty Officer 1st Class Russell Matthews suddenly showed up at his home Sunday night, CBS Honolulu affiliate KGMB-TV reports. An investigation is under way to figure out where Matthews has been and what he's been doing. Matthews, 36, was being investigated for illegal drug use when he disappeared. Early last October his car and slippers were found at the out-of-the-way area of Kaena Point. His hat was in the water. The Coast Guard searched 10,000 square miles during two days, but there was no sign of him.