> we write an encrypted private key to the note and don't keep a copy If the private key ever existed in your custody, there is no way to prove that it was not

> we write an encrypted private key to the note and don't keep a copy If the private key ever existed in your custody, there is no way to prove that it was not copied. Sorry. No amount of "trust us" is good enough here. Hell, you may not even know if it was copied if your process was compromised. The only way for a private key to be private is for it to never leave a secure device that generates it. (And even then, there are numerous caveats)