Ah, the Left Behind series ... Are you reading it in the King James or NASB version?
LOL! The Tim LaHaye version.
Then again in Luke it is written...."I tell you, in that night there shall be two men in one bed; the one shall be taken, and the other shall be left. Two women shall be grinding together; the one shall be taken, and the other left. Two men shall be in the field; the one shall be taken, and the other left. "
Which certainly would more than suggest some are 'left behind'.
BTW...There's a lot of Christians who have different opinions on a lot of this But I dont think we need to have on a boxing gloves....just saying.