Then take the same concept for the unconfirmed transactions after x amount of time instead & apply it.
So, if someone creates a transaction and it doesn't get confirmed right away, you're saying we should steal their bitcoins?
No thanks. Horrible idea.
If I broadcast a transaction that doesn't get confirmed, then I might want to spend those transaction outputs in a different transaction in the future. What right do you have to take my money just because you saw a transaction I created once in the past?
Just out of curiosity where do coins go then from sending to a none existing address?
It is not possible to send to a non-existing address.
Furthermore, at the protocol level there are no addresses and there are no coins. Those are abstractions that we humans use to make it easier to talk about the transfer of control over value. "Coins" never "go" anywhere. Transactions either exist in the blockchain or don't exist in the blockchain. The amount of "coins" you "own" is actually just the sum of the value of the transaction outputs in the blockchain that you have control over.
Do they just stay in an unconfirmed state?
Transactions are unconfirmed until they are either included in a block in the blockchain, or until they become invalid.
If so why can't the same method be applied?
Because bitcoin doesn't work the way you seem to think it works, and you haven't taken the time to learn how it actually works.