Is it possible that Jesus' second coming has already occurred, but the unchosen ones have been ignored to remain unaware?

ANYTHING is possible.

No it is not possible note of what Matthew 24 says “Immediately after the tribulation of those days, the sun will be darkened,+ and the moon will not give its light, and the stars will fall from heaven, and the powers of the heavens will be shaken.+ 30 Then the sign of the Son of man will appear in heaven, and all the tribes of the earth will beat themselves in grief,+ and they will see the Son of man+ coming on the clouds of heaven with power and great glory.+ 31 And he will send out his angels with a great trumpet sound, and they will gather his chosen ones together from the four winds, from one extremity of the heavens to their other extremity.

There will be change in the world so no Jesus hasn't came yet.

No the second coming will be extremely loud God's Angels will sound the trumpets to announce the imminent arrival of Christ.

He will return exactly the way the book of revelation says he will the armies of Heaven and the Saints will follow behind him.

No.

Revelation 1:7 KJV

7 Behold, he cometh with clouds; and every eye shall see him, and they also which pierced him: and all kindreds of the earth shall wail because of him. Even so, Amen.

At Christ's return, EVERY EYE will see Him. That means everyone will know. Straight out of the Word of God.

Luke 4:4 KJV

And Jesus answered him, saying, It is written, That man shall not live by bread alone, but by every word of God.

How many people on the planet today claim to be the second coming of christ. You'd' never know even if he really existed, for one, and came back, for two.

Yes, Jesus second coming occurred July 14, 70 AD. It even made it into the history texts.

Jesus has turned his attention to the earth totake out of it a people for God. When Jesus returns, everyone will know.

No it's not possible. Jesus is dead and will remain so, just like any other person.

It's possible that he himself is unaware. And may never become aware but most likely he will eventually

I've not seen a zombie except on Walking Dead.

We're only here for the second death.