You are 100% incorrect. If I were to say there is a tiger in your living room, you would be able to quickly prove or disprove that immediately. If I were to say there was a specific microorganism in your living room, you would not be able to empirically say it wasn't there just because you were unable to detect it. There are plenty of scientific theories throughout history that were later disproved. They could not be disproved at the time though because the lack of proof was not proof that it didn't exist.