None are left behind

2 Peter 3:8 But do not overlook this one fact, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day.

At the time the Apostle Peter wrote this letter the scoffers of Christianity were claiming Jesus wasn't coming back. And even today we have those same kind of scoffers. These scoffers naturally are those who openly reject Jesus because they don't want to give up what God says is sin.
Peter addressing the readers of this letter as beloved, is concerned about any effect the scoffers would have on fellow Christians.
A thousand years is as a day and a day is as a thousand years to God, because in heaven, or in eternity time is not an issue with God.
We humans are always trying to compare God to ourselves. The Bible says God is Spirit, so obviously we are flesh, and we age with the years. God is an eternal self existent being, time has no bearing, God created time.
What is left here is like Peter, God Loves mankind. God doesn't take any pleasure in the destruction of the wicked, or sinner's. God's desire is that all would turn from their sin and receive Jesus the Christ and be saved from the destruction of all who reject God's invitation into His Family through Jesus.
So whether it is another day or a thousand years, it is Our Father God's Love to make sure that all who will come to Jesus will come. With God none are left behind.
Well unless they choose to be.

Offer to God

Psalm 50:14-15 Offer to God a sacrifice of thanksgiving, and perform your vows to the Most High, 15 and call upon me in the day of trouble; I will deliver you, and you shall glorify me. #Bible

In the old testament offering God a sacrifice of thanksgiving wasn't just to say thanks, but it was accompanied with a animal sacrifice. It was to say thank you to God, but if you were really thankful, the animal proved it.
Performing your vows was like if you made a deal with God, your side of the agreement was to pay your vow again with sacrifice to show God you were really thankful for His help.
Israel had become robotic in this interaction with God, some say even to the point of helping God, by feeding the priests with their sacrifices. Even to the point that God should be obligated.
God simply wanted Israel to be sincere, to remember that they really are beholding to God for their very existence.
God says if you do these things, in the day of your trouble, He will deliver them, and because of your greatfulness you will glorify Him.
God wanted them to remember even when they didn't have trouble, but when they did, that God would listen to their call for help, and of their own volition glorify Him
Another point to be made here is that God even in this age was preparing Israel for the coming of the Messiah. When these sacrifices would no longer be the blood and flesh of animals, but the one and final sacrifice of the Son of God, who takes away the sin of all mankind who would look upon Him and believe. Jesus, who would be everything in what God the Father desires in relationship with Israel, and all of mankind.
So let's remember in our worship, our vows, and in our thankfulness, to be sincere expressing our desperate need for our LORD. Remember robots don't feel, they can't express, and they can't recognize who our Wonderful God is.