Oh no! This happened to a friend of ours exactly the same thing! She banned him literally weeks before the birth and told him she didn't want any money etc from him and he could not see his son..... I am like you and can see it as being suss....
Anyway I think he needs to speak to a family law specialists to understand his rights - which of course he has. Has she put him as the father on the birth certificate????
I am sure someone with more experience or advice will pop in here and let you know what he can do