I was under the impression that we have observed phenomenon that behave as we'd expect a black hole to behave. Since they behave like black holes, I believe it's reasonable to assume that they are black holes.
I am curious about your comment on speculation. It seems to imply that a question...
You cross the event horizon of a black hole and send that black hole traveling towards a star. When the black hole is in orbit around the star, you (assuming that you can) exit the black hole at the same time as when you entered it. What happens? Is that possible?
From what I understand...