Sending coins back to the address they came from could just end up losing the coins permanently, because now days wallets do not re-use addresses, and the original owned might not have that address in his wallet anymore.
I'm very interesting in this. Where do you find such kind of information? If you have seed, it will contain ALL addreses (used and not-used). With it you will be able to get access to any address which you were used.
You are correct, aplistir does not know what they are talking about. Modern HD wallets remember all used addresses.