This hasn't happened to me. However I have had a lot of contact with the police and as a result I did extensive research before ordering. Firstly SN isn't illegal. Ordering it isn't a crime. So while the police may come to your house, they won't arrest you. If they do come to your house without arresting you you can refuse to speak with them and ask them to leave. They cannot force you to do anything, they cannot enter your home without permission, and they cannot arrest you just for not wanting to speak to them.
Secondly, it's important to know the circumstances where they can arrest you. They would have to have evidence that you were planning on using the SN to commit a crime. This would be things like evidence of you threatening to poison someone or something that links you to criminal activity. If they don't have that they cannot charge you with a crime.
Thirdly, in the unlikely event of an arrest, please please please do not say anything to them and request a lawyer immediately. This is very standard and does not make you look guilty. They cannot presume guilt just because you exercise your right to legal counsel. They will hold you for 24 hours regardless, so if they say anything like finding you a lawyer will delay things, they are lying in order to make things easier for themselves. It happened to me and it is unfortunately very common. Even if you think you don't need a lawyer because you already know to say "no comment" to everything, it's important because they will be able to explain to you exactly what is happening.
As for me personally I have ordered my SN under a pseudonym so I'm hoping if they do seize it they won't trace it back to me. Given my history they almost certainly would think I was planning a crime and I would have no defence.
