Technically, if someone falls away from the faith, they either did not have salvation previously or else they lost salvation when they lost their faith.
The argument of which one it is seems to me to be a moot point. For, either way, if someone does not have faith in the present moment, they do not have salvation in the present moment. This is agreed to by both the Arminian viewpoint and the orthodox Calvinist viewpoint.
There is also an unorthodox OSAS viewpoint that says you will continue to have salvation even if you lose faith.
That is not a scriptural viewpoint...it is even a heinous doctrine of devils.
For we have access by faith into this grace wherein we stand (Romans 5:2) and we are saved by grace through faith (Ephesians 2:8).
Therefore, if we do not have faith, we do not have access to grace and are therefore not saved.
Whether we were saved before or not is not the issue.
Let's try of focus on what is important...exhorting the unbeliever to have faith in Jesus.