A quick google didn't reveal much, apparently some guy just bought out a book about the VIP muscle, some people say that it doesn't actually exist in humans and it's the Vastus Intermedius Profundus muscle which is only found in animals and that the book is a scam, some people say it's actually the pubococcygeus. I hadn't heard of it before your mention of it but google usually throws up something informative, in this case there wasn't much to look up.
