Hi!
As the title says, what happens if i get an address wrong? Do the coins get lost?
If that's what happens, why not change the code in Bitcoin, so that if the bitcoin network cant detect that address, returns the bitcoins to you?
If the transaction does not find the destination within a certain time, then the cashback. That's what I know but I think you should think about risk you may not get cashback if the address you send has a user.