question:  Which theory didn't they rule out for how Superior went missing?
context: Radio messages stated simply that Superior had seceded from Earth. But Don Cort, stranded on that rising town, was beginning to suspect that nothing was simple about Superior except its citizens. The state police converged on the former site of Superior from several directions. Communicating by radiophone across the vast pit, they confirmed that the town undoubtedly was missing. The train's schedule called for it to pass through but not stop at Superior at 11:58. A National Guard officer volunteered to take a jeep down into the pit, having found a spot that seemed navigable. The Pentagon and the Atomic Energy Commission denied that they had been conducting secret experiments. A United Airlines pilot found Superior early on the morning of November 1. The object loomed out of a cloudbank at twelve thousand feet and Studley changed course to avoid it. He noted with only minimum satisfaction that his co-pilot also saw the thing and wondered why it wasn't moving at the terrific speed flying saucers were allegedly capable of. A few minutes later he had relayed a message from Superior, formerly of Ohio, addressed to whom it might concern: It said that Superior had seceded from Earth. One other radio message came from Superior, now airborne, on that first day. Don Cort had been dozing in what passed for the club car on the Buckeye Cannonball when the train braked to a stop. Don made his way up to the locomotive and found a bigger knot of people gathered in front of the cowcatcher. Don saw two men who must have been the engineer and the fireman talking to an old bearded gentleman wearing a civil defense helmet, a topcoat and riding boots. Nevertheless, Don could see that it apparently was a neat, sharp edge, not one of your old ragged, random edges such as might have been caused by an explosion. "If what Mr. Cort and the fireman say is true. Well, Professor Garet telephoned and said, 'Hector'—that's my name, I think what he was trying to convey was that this—this levitation confirmed his magnology principle."
output:  magnetized levitation
options:  secret government experiments  explosives  factory explosion  magnetized levitation