To fake a rapture would not work because it could not simulate the absence of the people. I could see terrifying the true Christians for a very short time, but too short for real spiritual damage. You would very soon realise that all the normal day events are all present. At work, at the airports, and everywhere else on the planet everything would be rolling as normal. I don't think the dark side is going to use a loser plan like a fake rapture. Bottom line is, you would see that no one is missing in too short of a time.