The rapture will not be a secret - it will occur with a lot of commotion including a shout and a trumpet and the voice of the archangel. As lightning flashes in the east is seen in the west. The first verse in the following passage from Matthew 24 shows it's visible and the last verse is the rapture itself:

27 For as the lightning cometh out of the east, and shineth even unto the west; so shall also the coming of the Son of man be.
28 For wheresoever the carcase is, there will the eagles be gathered together.
29 Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken:
30 And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory.
31 And he shall send his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other.

All occurs "immediately after the tribulation"

"from the four winds" come those of us who are still alive at the time.
"From one end of heaven to the other" come the dead in Christ who rise first.