Are the unredeemed found to be "in Christ?" Can you show me scripture where they are found in Christ?
You point out precisely why it is impossible for men to have been born again in the Old Testament: they all died awaiting Eternal Redemption.
Which was accomplished by Christ:
Hebrews 9:12-15 King James Version
12 Neither by the blood of goats and calves, but by his own blood he entered in once into the holy place, having obtained eternal redemption for us.
13 For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh:
14 How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God?
15 And for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance.
Because Hebrews is specific to Hebrews, the transgressions of the Law are said to be redeemed by Christ's Offering. His Redemption is also meant for those prior to the establishment of the Covenant of Law.
The promise of God to forgive sin in an eternal context (forever) is part of the promise of God in regards to the day He would establish a new Covenant:
Hebrews 10:15-18 King James Version
15 Whereof the Holy Ghost also is a witness to us: for after that he had said before,
16 This is the covenant that I will make with them after those days, saith the Lord, I will put my laws into their hearts, and in their minds will I write them;
17 And their sins and iniquities will I remember no more.
18 Now where remission of these is, there is no more offering for sin.
And the New Covenant had no power and was not in force as long as the Testator (Christ) was still alive:
Hebrews 9:16-18 King James Version
16 For where a testament is, there must also of necessity be the death of the testator.
17 For a testament is of force after men are dead: otherwise it is of no strength at all while the testator liveth.
18 Whereupon neither the first testament was dedicated without blood.
So as I said, your statement makes the point men were not regenerate in the Old Testament:
Mark 10:18
And Jesus said to him, “Why do you call me good? No one is good except God alone.
Are the unredeemed found to be "in Christ?" Can you show me scripture where they are found in Christ?
There are none good except God.
There are none righteous except God.
No, not even one.
That is why men still have to be redeemed through the Sacrifice of Christ. That is why even the transgressions of the Old Testament Saint remained unredeemed, because Christ had not yet atoned for them. That is Paul's point here:
Romans 3:20-26 King James Version
20 Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin.
21 But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets;
22 Even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe: for there is no difference:
23 For all have sinned, and come short of the glory of God;
24 Being justified freely by his grace through the redemption that is in Christ Jesus:
25 Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God;
26 To declare, I say, at this time his righteousness: that he might be just, and the justifier of him which believeth in Jesus.
Abraham's deeds were accounted to him righteousness. By deeds, I refer to his belief and faith (and in that order). Those are something Abraham did.
Dying on the Cross is something Christ did. Alone. Because His disciples fled and abandoned Him.
That is how one can be declared righteous under an Old Testament standard and still be counted with those who are not righteous, and that is everyone that has not had the righteousness of Christ imputed to their behalf.
Every passage above shows that Christ's death and the Redemption He obtained for us is distinct from Old Testament Economies.
When did Christ's righteousness begin to be declared? It wasn't before His death, because the Gospel was a Mystery not revealed to the sons of men, past Ages, or past Generations.
That seems pretty all-inclusive to me. Hence, "There is none righteous, no, not one."
We know men were not in Christ even up to the point of His death, and including His disciples. This is according to His Word in John 14:15-23.
Men who are not in Christ are not regenerate. No man was in Christ until Pentecost.
No man was regenerate in the Old Testament.
God bless.