General warning: do not formally seek permission BEFORE you have a book contract.
Yes, this. Seeking permission includes stating who is going to publish the image, when, and for what purpose. You don't know any of that until you have a contract. What you want to be doing now is locating images that you would be able to use.
As for your own photos, you can take those anytime, provided that's okay with the museum, and provided there is not a fee! You don't want to get into paying for images or permissions before you have a contract, for obvious reasons. Many museums don't allow you to photograph, but you can always speak to this person, discuss your project, and ask.
I'm sorry if I'm misinterpreting your question, but are you asking how to contact this man in advance since you cannot find email, website, etc? Is the collection in his private home, and therefore you can't just go to the "building" and see the hours posted? I'm assuming here that this museum is in your city. How about working through the reporter who wrote about the collection? If the man considers this a museum, I'd think he'd be open to public viewing. Was that info maybe published along with the reporter's article?
I hope this is of some help.