Oh I completely agree with that. Funny though that on one hand people say "lost and found" indicates salvation, but then you say that words don't have to exactly match up....
What is true however is that even if words do not match up, concepts do. And all the "players" in the parable (coins, sheep, people, etc) represent something. So if the younger brother is supposed to be a picture of a lost person who is then found, what picture is the older brother supposed to be? The older brother is a important reason why I do not hold this parable to equate to salvation. Also the fact that we have the younger brother going through 3 different states: Safe, part of the family, has inheritance / in the wild, with the pigs, squanders inheritance / returns to family, part of the family, safe. There are different terms that could be used but that does indicate the different states. But the older brother remains in the first state and never changes.