First, God is in control of life and death. So there are no accidents. God knows the day of your death and He is in control ultimately. Second, coveting is a desire to have something of your neighbors and it does not mean you cannot desire certain things if you see them. For example: If Bob has a ham sandwich, and you would like to have one like his, it is not wrong to go and get one because you seen his. It would be wrong if you wanted only Bob’s ham sandwich and not another one. Coveting is desiring something that only that person has. Three, a Christian generally should not want to seek out a flashy vehicle that is highly admired by others (i.e., an object that is known for loving the world), and is known for speeding (i.e., breaking the Law). 1 Timothy 6:10 says we are not to covet after being rich or having lots of money (i.e., the love of money). Chasing after riches is not for the Christian life and so one would be coveting (desiring) something that God does not desire for us. 1 Timothy 6 warns us not to even fellowship with other believers who are like a Joel Olsteen (i.e., a prosperity believer).
In any event, to get to the point of your story: If this professing believer truly committed the sin of coveting in God’s eyes, and they died without having confessed of that sin, then they would be cast into outer darkness (being reserved for the Judgment and the Lake of Fire). Why? There could be several reasons. One potential reason is that they had an evil heart and they preferred sinful things rather than the things of God. Meaning, they are double minded. Another reason is that this person rejected the Scriptures teaching that you have to confess and forsake sin in order to have mercy (Proverbs 28:13). They don’t really believe the Bible’s teaching on Conditional Salvation. So naturally they will turn God’s grace into a license for immorality on some level teaching you can sin and then die and be saved by His grace (i.e., a justification to sin). Jude 1:4 warns against those who turn His grace into a license for immorality. The KJB says lasciviousness. The Parable of the Prodigal Son is proof you can go from a saved state, to a lost state, and back again to a saved state. In the Parable, when the prodigal son comes home seeking forgiveness of his sins with his father, the father says that he was “dead” and he is “alive AGAIN.” Seeing the son did not die physically, the parable is speaking in spiritual terms. The son died spiritually when he was living it up with prostitutes, and he became alive AGAIN spiritually when he came back home and sought forgiveness with his father. This is a parallel of how we are to seek forgiveness with our EVERLASTING father named Jesus Christ. Jesus even warned against how looking upon a woman in lust can cause our whole body to be cast bodily into hellfire (Matthew 5:28-30). Where was Unconditional Eternal Security in that situation? There wasn’t any because it is a false doctrine. Only Conditional Eternal Security is true. We are only eternally secure if we abide by the conditions God gives us in His Word.