That may not be correct.
He has to tell them not to mourn:
Jn 14.18 ¶ I will not leave you comfortless: I will come to you.
27 Peace I leave with you, my peace I give unto you: not as the world giveth, give I unto you. Let not your heart be troubled, neither let it be afraid.
The apostles expected Him to return immediately.
Where do these verses state that Jesus would immediately return???
Do not be troubled, Jesus will be with us always. This is not understood until after the Resurrection. Of course Jesus is trying to comfort them prior to the Resurrection, when they know He must go to the cross, and they have no clue about "rising from the dead" yet.
Therefore, they stood gazing up into heaven. He didn't return then, but the words of v11 leave no doubt that He will return, and hasn't done so yet:
11 Which also said, Ye men of Galilee, why stand ye gazing up into heaven? this same Jesus, which is taken up from you into heaven, shall so come in like manner as ye have seen him go into heaven.
He has "gone to the Father to sit at His right hand", but God is not literally "sitting" anywhere, since He is everywhere. It is a position of power and authority. Jesus "went to the Father" as an indication of His glory and power. He remains to us, present, just as God the Father, as He promised to be with us always
Jesus states this in Matthew just before His Ascension...
I am with you always, even unto the end of the world. Mat 28:20
Therefore:
1 The same Jesus
2 Will come as visibly as He went into heaven, ie 'with clouds'
He has not manifest Himself in THAT manner, but it doesn't follow that He is not present even now!!!
He will make Himself manifest. Now, He is invisible. Just as at the Transfiguration, Moses and Elijah were made manifest, made visible. That Jesus left and is "not here" does not explain their joy... The joy is only explained by the fact that He would be with them always, even if not VISIBLY manifest. He is with us through the breaking of the bread, through the Word, through other Christians whom we meet.
Any suggestions that He is already here, or returned in the 1stC are therefore wrong. As Rev 1 says...
7 Behold, he cometh with the clouds, and every eye shall see him: and they also that pierced him. And all the tribes of the earth shall bewail themselves because of him. Even so. Amen.
Of course, visibly seen, see above. Jesus, being True God and True Man, can be present here among us in a form that we do not recognize, just as the Apostles did not recognize the Christ immediately following the Resurrection. Jesus said "where two or more are gathered in together in my name, there I am in the midst of them ". Matthew confirms this in the last sentence of his gospel. He is invisibly present to us, right now. Thus, Jesus can tell Saul "Saul, Saul, why do you persecute ME"...
Jesus is present and abides in those who are "in Christ", buried with Him through Baptism. Thus, the Good News - Jesus REMAINS present to us! At the end, He will manifest Himself for all to visibly see.
Regards