Couldn’t 4:15’s “who are left till the coming of the Lord” refer to those left after the tribulation when Jesus returns? I’m only aware of one return and that is at the Revelations 18/19 and Matthew 24. So doesn’t 4:15 refer to that?
I’ve no investment in rapture discussions as I’m a firm believer in Matthew 24:36 and 24:42....I’m never going to know the time nor am I supposed to.
But Matthew sure seems to put any taking post tribulation as I read chapter 24:29-31 “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: And then 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: 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. And he shall send his angels with a great sound of trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other.” And those are HIS words.
The Rapture cannot be considered a "return" because Christ does not come to earth at that event but catches His bride to Himself and takes us back to "where He (is)", which is Heaven. So the Rapture is not a return of Christ.
And no, neither you nor I nor anyone will know the day or the time of the Rapture, but Jesus does command us to watch for Him as we see the prophesied signs He gave coming to pass, and we are to know the season we are in. That is a commandment.
And the passage you gave from Matthew is proof positive of a pre-trib Rapture - in the Rapture Christ Himself comes for His bride; after the Tribulation is complete, He sends angels to collect those who have become saved during the Tribulation.
Two separate events, with two separate methods of collecting His own.