Will all that are lost be saved?

In Luke 15 , Jesus gives one parable of a man that lost 1/100 sheep, and rejoiced when that sheep was found. And another parable of a woman who lost 1/10 silver coins, and rejoices much when she finds her lost coin. In order for something to be "lost", it must be in one's possession at some point beforehand; and these parables confirm that in the sense of salvation. So, in regards to this, I have a two part question: Will all that are "lost" be saved? And in what sense were we previously in the Father's possession? Is there any scripture that talks about this? I know my 2nd question could mean those who had previously come to God, but have fallen away, and came to God *again*, but I think He is particularly talking about those who have not yet come to God. I think this could be clarified when Jesus says He came to seek that which was lost in relation to a Chief tax collector.