How long ago did this happen? If it was a while back, and you didn't find out from them directly ... maybe they are not as good as a friend as you thought they were?
They did tell me that the business was working well. I didn't care to ask how much they made from it, and it is public knowledge at this point, I just never bothered to look it up.
To me that sounds like they are a good friend who wants to be open but doesn’t want money to come between you two. One could quibble with that decision but it sounds better than a lot of other approaches.