According to an unconfirmed report, a thing happened Monday, though experts say it is still not clear exactly what the thing was. 'All we know at this time,' University of Prague professor of phenomenology Rupert Heiden said, 'is that some kind of thing happened.' Ordinary citizens, meanwhile, are struggling to put the thing into proper perspective. 'You just don't expect a thing like this to happen,' Stockton, CA, resident Pamela Worthington said. 'Not with things the way they've been.' In a statement released late Tuesday, President Clinton urged all Americans to remain calm and allow things to take their natural course. 'These things happen,' he said. 