CommentStreams:9235b0e2900918f3f6656d04cd2c8a1d
From The Lost Media Wiki
It looks like the author, J Gordon Melton, is still alive, so it should be possible for someone to reach out to him or his agent for some answers. He did write the book in the early 90s, so I wouldn't be surprised if he doesn't remember something he wrote close to 30 years ago. However, after seeing his Wikipedia page, he wrote another book on the topic of vampirism back in 2016 that he collaborated on with another author. It's available for reading on Google Books, however, the section for vampires and cinema is only up in bits and pieces, so you'll have to check the book out or buy a copy to see what it covers with the silent era.
I'm not sure if Melton has social media prescence either, so that's something we'll have to look into.