Sure. First off, and please don't take offense to my opinion and take on this, but I think you are slightly off base in your reasoning IMO.
I take no offense. Rather, I very much enjoy the give & take. Thanks for your well-worded explanation.
However, we may have to agree to disagree on this. My belief (as I'm sure your's) in "once/always saved" is set in bedrock.
Romans 6
Dead to Sin, Alive in Christ
1What shall we say, then? Shall we go on sinning so that grace may increase? 2By no means!
We died to sin; how can we live in it any longer? 3Or don't you know that all of us who were baptized into Christ Jesus were baptized into his death? 4We were therefore buried with him through baptism into death in order that, just as Christ was raised from the dead through the glory of the Father, we too may live a new life.
5If we have been united with him like this in his death, we will certainly also be united with him in his resurrection. 6For we know that
our old self was crucified with him so that the body of sin might be done away with,[a] that we should no longer be slaves to sin 7because
anyone who has died has been freed from sin.
8Now if we died with Christ, we believe that we will also live with him. 9For we know that since Christ was raised from the dead, he cannot die again; death no longer has mastery over him. 10The death he died, he died to sin once for all; but the life he lives, he lives to God.
11In the same way, count yourselves dead to sin but alive to God in Christ Jesus. 12Therefore do not let sin reign in your mortal body so that you obey its evil desires. 13Do not offer the parts of your body to sin, as instruments of wickedness, but rather offer yourselves to God, as those who have been brought from death to life; and offer the parts of your body to him as instruments of righteousness.
14For sin shall not be your master, because you are not under law, but under grace.
Slaves to Righteousness
15What then?
Shall we sin because we are not under law but under grace? By no means! 16Don't you know that when you offer yourselves to someone to obey him as slaves, you are slaves to the one whom you obeywhether you are slaves to sin, which leads to death, or to obedience, which leads to righteousness? 17But thanks be to God that, though you used to be slaves to sin, you wholeheartedly obeyed the form of teaching to which you were entrusted.
18You have been set free from sin and have become slaves to righteousness.
This is why I think in your example, he was never saved to begin with.
From Matthew Henry's Commentary regarding the above Scripture:
He argues from the precious promises and privileges of the new covenant, Romans 6:14. It might be objected that we cannot conquer and subdue sin, it is unavoidably too hard for us: "No," says he, "you wrestle with an enemy that may be dealt with and subdued, if you will but keep your ground and stand to your arms;
it is an enemy that is already foiled and baffled; there is strength laid up in the covenant of grace for your assistance, if you will but use it.
Sin shall not have dominion." God's promises to us are more powerful and effectual for the mortifying of sin than our promises to God. Sin may struggle in a believer, and may create him a great deal of trouble, but it shall not have dominion; it may vex him,
but shall not rule over him.
Also this:
Romans 8
35Who shall separate us from the love of Christ?
38For I am convinced that neither death nor life, neither angels nor demons, neither the present nor the future, nor any powers, 39neither height nor depth, nor anything else in all creation, will be able to separate us from the love of God that is in Christ Jesus our Lord.