The manner in which He left was visibly and bodily. They literally saw Him ascend bodily towards heaven. He has not yet descended bodily and visibly from heaven. You are deceived by the false doctrine of full preterism. It's heresy to not believe in the future glorious visible and bodily appearing of our Great God and Savior Jesus Christ.
You need to change your mind about this.
A full preterist believes what you believe. That Jesus Christ already returned and is not returning in the future.
Then you are a heretic because He most certainly is coming back in the future. You deny our blessed hope, the future appearing of our great God and Savior, Jesus Christ.
Titus 2:11 For the grace of God has appeared that offers salvation to all people. 12 It teaches us to say “No” to ungodliness and worldly passions, and to live self-controlled, upright and godly lives in this present age, 13 while we wait for the blessed hope—the appearing of the glory of our great God and Savior, Jesus Christ, 14 who gave himself for us to redeem us from all wickedness and to purify for himself a people that are his very own, eager to do what is good.
1 John 3:1 Dear friends, now we are children of God, and what we will be has not yet been made known. But we know that when Christ appears, we shall be like him, for we shall see him as he is.
Are you like Him yet with a glorified, immortal body? No. So, He is not come back yet. When He does, we will see Him as He is and will be made to be like Him with a glorified, immortal body. That will happen at the last trumpet (1 Corinthians 15:50-54).