No one saw Jesus leave, other than His disciples...
:23 But take ye heed: behold, I have foretold you all things.
00526 13:24 But in those days, after that tribulation, the sun shall be darkened, and the moon shall not give her light,
00527 13:25 And the stars of heaven shall fall, and the powers that are in heaven shall be shaken.
00528 13:26 And then shall they see the Son of man coming in the clouds with great power and glory.
00529 13:27 And then shall he send his angels, and shall gather together his elect from the four winds, from the uttermost part of the earth to the uttermost part of heaven.
Now one might try to argue that it says heaven and earth and it does but ewe must remember that Paul stated that absent from the body is presence with the Lord. So there are the spiritual and physical believers being gathered together to have their new incorruptible bodies.