But, God's word warns that a blood-bought child of the living God
CAN (i.e. is able to) lose that which he/she never had the power to gain.
No it does not.
Again, per John 6:37-40, not one of His actual sheep will be lost.
But many who think that they are saved will later find that they were never born again, were never foreknown, predestinated, called, justified and will never be glorified ( Romans 8:29-30 ).
Instead of being vessels of mercy afore prepared unto glory, they are vessels of His wrath fitted to destruction ( Romans 9:14-24 ).
Or, God is a liar (because of what He has clearly taught in His NT).
God, who cannot lie, promised those that truly believe on His Son
eternal life ( not "probationary" life ), and has saved us and called us with an holy calling...
Which was given us in Christ Jesus
before the world began ( 2 Timothy 1:9 ).
A father can give a gift to his son, and then proceed to take it back (for some reason).
E.G. a BB gun.
But not God the Father, whose gifts and calling are without repentance ( Him taking those gifts back, Romans 11:29 ).
He is not like human fathers, who can and do make mistakes and can and do take gifts back because sinful men ( and women ) can be capricious.
In addition, His true children cannot forfeit their salvation by already-forgiven sins ( Colossians 2:13-14 )...
Sins that are remembered by Him no more ( Hebrews 8:12, Isaiah 43:25, Jeremiah 31:34, Micah 7:18-19, Hebrews 10:17 ).
But those who profess Him with the lips while their hearts are far from Him, can and will be judged for their sins;
Sins that were never washed away by the blood of His dear Son.