I'm resubmitting a question I previously asked, but crystalising it down to its 'simplest' form.
In a multisite network, how can one get the blog_id for where a post was originally published from?
It's a simple question that should have a simple answer. We're trying to determine the post's blog_id from outside its originating blog (i.e. from another network blog or the main parent blog), so need some way of supplying an argument such as post_id.