well i was mostly wrong! just had a look at a web page i just found
The Rapture Theory: It's Surprising Origin since i could only remember bits and pieces of this documentary.
apparently christ does come back (invisibley of course!) to save all christians.
according to this and a few other pages i looked at the rapture isnt from the bible, but many sections from the bible have been taken and put together to end up with this theory.