A Florida state investigator has reported that two days before David Kennedy's drug-related death in a West Palm Beach hotel, Kennedy wrote a $120 check to a former bellhop accused of selling him cocaine. The investigator made the finding by analyzing handwriting impressions in Kennedy's checkbook . . . Britain's Prince Andrew is to return to the Falkland Islands next year for a five-month navy tour of duty. Queen Elizabeth's second son is a lieutenant who served there in 1982 during the war with Argentina. He will be flying a helicopter patrol over the 200-mile protection zone around the disputed islands . . . The White House press offices were having their share of calls yesterday from journalists who were not concerned about "A" or "B" list parties. They were concerned they hadn't been invited to either . . . When Mike Hammer's creator Mickey Spillane was asked by a New York Post reporter what he thought about television's Stacy Keach's jail sentence for cocaine possession, he said: "All I can tell you is Mike Hammer would never have got himself caught in a mess like this" . . . Where have all the bobby-soxers gone?Frank Sinatra turned 69 yesterday . . . Ray Calamaro, a former assistant attorney general under Griffin Bell, and Peter Gold, Sen. Gary Hart's former chief legislative aide, are opening the Washington office of the Wall Street firm of Winthrop, Stimson, Putnam & Roberts . . . Former HHS secretary Richard Schweiker has been elected to the board of directors of the National Medical Enterprises . . . It's Christmas time and a troop of little Brownies came to Washington from Manhattan yesterday to put a winning ornament on the New York Christmas tree on the Ellipse in a Hallmark Cards Girl Scout Council contest. The winning motto on the popcorn globe was: "I wish the world was made of candy, a million dollars would be handy. Everyone could have a pup, and kittens would never grow up." It's hard to argue with such sentiments . . .