First you have to know what the Rapture is. Its a belief of some Christians that before the Great Tribulation, a period of seven years leading to the war called Armageddon, Christians will leave the planet and spend this time in heaven with Jesus.
Its a commonly known belief. Those that do not except this view say "If a bunch of Christians disappear then everyone will know what's happening."
I know why they won't know. In fact when this event happens Christian leaders will swear that the disappearance has nothing to do with the Bible.
Why will there be Christian leaders left behind to make this evaluation? Because you get what you believe and most of them don't believe in a pre-Trib Rapture. A lot of them are simply fake Christians.
Don't get confused, this is not an evangelistic thread. This is a conspiracy thread. This thread will be full of heresy and yet it will be true.
You won't be able to find this secret in books or on the net, only here.
So, should I go on, or are you sick of the subject already?
"God is not the author of confusion, but He is the author of mystery, and mystery can be very confusing." old wayne5 saying.