People are NOT going to know that billions of Christians have gone. How many people will know if YOU had been taken? Only a few. And if many so called believers are not eagerly awaiting the Lord they will not be ready. Plus there will be the war in the mountains of Israel where God deals with the northern army. So people will be glued to their T.V. etc
There are many people missing daily and moving house and being killed, that some believers not there will not be a big thing. Families may only think they had gone on a holiday or are just missing.
The dead in Christ will rise first. The resurrection is the real focus of prophecy.
Concerning that northern army;
20 The fish of the sea and the birds of the heavens and the beasts of the field and all creeping things that creep on the ground,
and all the people who are on the face of the earth, shall quake at my presence.
And the mountains shall be thrown down, and the cliffs shall fall, and every wall shall tumble to the ground.
21 I will summon a sword against Gog on all my mountains, declares the Lord God. Every man's sword will be against his brother.
22 With pestilence and bloodshed I will enter into judgment with him, and I will rain upon him and his hordes and the many peoples who are with him torrential rains and hailstones, fire and sulfur.
23
So I will show my greatness and my holiness and make myself known in the eyes of many nations.
Then they will know that I am the Lord.
Ez 38
No secret return exists in scripture.
5 It is clear evidence of God’s righteous judgment that you will be counted worthy of God’s kingdom, for which you also are suffering,
6 since it is just for God to repay with affliction those who afflict you 7 and to give relief to you who are afflicted, along with us. This will take place at the revelation of the Lord Jesus from heaven with his powerful angels, 8 when he takes vengeance with flaming fire on those who don’t know God and on those who don’t obey the gospel of our Lord Jesus. 2 Thess 2
29 “Immediately after the distress of those days, the sun will be darkened, and the moon will not shed its light; the stars will fall from the sky, and the powers of the heavens will be shaken. 30 Then the sign of the Son of Man will appear in the sky, and then all the peoples of the earth will mourn; and they will see the Son of Man coming on the clouds of heaven with power and great glory. 31 He will send out his angels with a loud trumpet, and they will gather his elect from the four winds, from one end of the sky to the other.
Matt 24