The more important question is what will be done to prevent this from happening again to somebody else (obviously this doesn’t need a response here, I assume an internal investigation is underway and this will be publicly communicated after its complete).

Hi John, your website's contact link is pointing to your twitter account and you don't have messages opened.

What is the best email to reach out to you?

Thank you.

How was he supposed to know to email you?

I don't think he's saying that OP should've known to email him, just that he would've done the same thing over private emails where nobody was watching, as he is doing here publicly.