I figured it out from a post of his where he links to an article and says that Simon singh said that I introduced him to something.. and then the article quotes

I figured it out from a post of his where he links to an article and says that Simon singh said that I introduced him to something.. and then the article quotes Simon as saying David Hayes did that thing. It's easy to find these things, especially with somebody who's been in computing for so long and probably has a huge digital trail and no desire to hide their identity. If I didn't see anything in 30 seconds of browsing his post history, next step would be to look up the authors of the papers quoted in the Bitcoin paper(not many) and see if any are still living and interested in astronomy, based on his username.