For what is our hope, or joy, or crown of rejoicing? Is it not even you in the presence of our Lord Jesus Christ at His coming?
I Thessalonians 2:19
The apostle Paul is referring to that day when the Lord comes for the Church and believers have that great meeting in the clouds (1 Corinthians 15:51; 1 Thessalonians 4:15).
Paul recognized that he would most likely never see those at the Thessalonian Church in the flesh again but the moment they came into the presence of the Lord in that meeting in the clouds Paul would not only see them, he would know them.
We too will see and know our loved ones when the trumpet sounds and all believers of this age of grace dead and those alive will meet the Lord in the clouds.
‘For if we believe that Jesus died and rose again, even so God will bring with Him those who sleep in Jesus. For this we say to you by the word of the Lord, that we who are alive and remain until the coming of the Lord will by no means precede those who are asleep. For the Lord Himself will descend from heaven with a shout, with the voice of an archangel, and with the trumpet of God. And the dead in Christ will rise first. Then we who are alive and remain shall be caught up together with them in the clouds to meet the Lord in the air. And thus we shall always be with the Lord. ‘
I Thessalonians 4:14-17