So the bitcoins returned to 1NxmG7uszkcUKgNEbvjrxmvajepMgdVg8S?
How the owner of 1NxmG7uszkcUKgNEbvjrxmvajepMgdVg8S can avoid this situation in the future?
And this other transaction
https://blockchain.info/tx/3538fa649cecf188fbfd4afc5722b019f57ed9fa28138c3f1ea180f4ac8fcf32 is to other address, with other value an in other date, why this invalidate the first transaction?
Sorry for these questions, I'm newbie in bitcoin.