As soon as you take the powder out of her pocket, you are in possession of a Class A drug. You do not have lawful authority to possess the drug, therefore you are committing the offence of possession of a Class A drug. There are defences in law to possession. In this case, you have a defence if you intend to pass the drug to the police as soon as possible or dispose of the drug as soon as possible. This does not mean hanging on to it till the end of the shift. It means quickly! If, having taken possession of the Class A drug, you give it to someone who cannot lawfully possess the drug, then you are guilty of supplying a Class A drug. It is possible to be found guilty of supplying someone with their own drugs. There are stated cases - trust me. You have only two choices - you dispose of it immediately or you get your control room to get the police to join you. Anything else would leave you open to all sorts of nastiness. Patient confidentiality is not an issue.