Backsliding does NOT result in loss of Salvation. It always results in chastisement and sometimes results in wickedness.
1 Co 5:1-5
It is reported commonly that there is fornication among you, and such fornication as is not so much as named among the Gentiles, that one should have his father's wife.
2 And ye are puffed up, and have not rather mourned, that he that hath done this deed might be taken away from among you.
3 For I verily, as absent in body, but present in spirit, have judged already, as though I were present, concerning him that hath so done this deed,
4 In the name of our Lord Jesus Christ, when ye are gathered together, and my spirit, with the power of our Lord Jesus Christ,
5 To deliver such an one unto Satan for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus.
KJV
If we backslide so as to compromise our testimony or the testimony of the church; we may be called home early, and perhaps painfully or unpleasantly; but even then salvation is NOT lost.
According to the bible, backsliding most certainly leads to the loss of the promise of salvation.
In the passage you cited above the man backslide into fornication, a lost condition, Gal 5:19-17 those that commit fornication, such shall
NOT inherit the kingdom of God. He must repent or perish, Lk 13:3,5, they were to withdraw and dis-fellowship this man and 2 Cor 2:6,7 indicates they did and this man repented.
2 Tim 4:4 "
And they shall turn away their ears from the truth, and shall be turned unto fables."
Some backslide from the truth that saves unto fables that do not save. "
Brethren, if any of you do err from the truth, and one convert him; Let him know, that he which converteth the sinner from the error of his way shall save a soul from death, and shall hide a multitude of sins." Again, a
brother can backslide from truth to error and becomes lost unless that '
sinner' converted and saved from spiritual death. (He goes from a brother to a lost sinner needing to be converted again.)
The one sheep backslides from the 100 becoming "
lost"
the prodigal backslide in spending money on harlots becoming "
dead"
some backslide due to
unbelief, Heb 4:11 cf Jn 3:18
Peter speaks of those Christians that backslide to hogs wallowing in the mire/dogs return to eating own vomit,
denying the Lord that bought them 2 Pet 2:1.
Each and every case cited above the promise of salvation was lost unless the person(s) involved CONDITIONALLY repented/converted back.
In some cases no repentance/conversion takes place and some disciples are gathered as branches and cast into the fire, Jn 15:1-6; Judas the apostle
is lost, Jn 17:12; some disciples turn to follow no more, Jn 6:66.