But the father did not go out and seek his prodigal son.
Another thing, are you saying the saved sheep can be lost?
Yes, but not permanently lost, their being lost is just temporal or of relating to a period of time in their earthly existence.
That they are always Christ's sheep is true in that God has known them before He made of them physical creatures in this reality, in this age.
But they were still born into this world and so then being born will fall into sin, so they have need of a savior redeemer who is actually their near kinsman who will pay the price for the redemption of His family members. They were known to God beforehand as sons and daughters, brethren, the children of God.
The children of God have partaken of flesh and blood and He has also partaken of the same as His brethren to aid to salvation those who are 'of the seed of Abraham', not to those who are of the seed of the world who are the seed (children) of Satan.
Jesus told us that some have Satan as their father and they are his children and desire to the deeds of their father the devil, John 8.
The parable of the wheat and the tares fully describe this spiritual reality.
In the field of the Lord, do you agree that some are planted by God, as the good seed and some are planted by Satan, the weeds tares among the wheat?
Matthew 13:24
[
The Parable of the Wheat and the Tares ] Another parable He put forth to them, saying: “The kingdom of heaven is like a man who sowed good seed in his field;
Matthew 13:25
but while men slept, his enemy came and sowed
tares among the wheat and went his way.
Hebrews 2
Bringing Many Sons to Glory
10 For it was fitting for Him, for whom
are all things and by whom
are all things, in bringing many sons to glory, to make the captain of their salvation perfect through sufferings. 11 For both He who sanctifies and those who are being sanctified
are all of one, for which reason He is not ashamed to call them brethren, 12 saying:
“I will declare Your name to My brethren;
In the midst of the assembly I will sing praise to You.”
13 And again:
“I will put My trust in Him.”
And again:
“Here am I and the children whom God has given Me.”
14 Inasmuch then as the children have partaken of flesh and blood, He Himself likewise shared in the same, that through death He might destroy him who had the power of death, that is, the devil, 15 and release those who through fear of death were all their lifetime subject to bondage. 16 For indeed He does not give aid to angels, but He does give aid to the seed of Abraham. 17 Therefore, in all things He had to be made like
His brethren, that He might be a merciful and faithful High Priest in things
pertaining to God, to make propitiation for the sins of the people.18 For in that He Himself has suffered, being tempted, He is able to aid those who are tempted.