a black hole in such a universe would have a 3-d "surface"
I'm trying to decide whether this makes any more sense than a square circle. 3D surface is a contradiction in terms. A surface is 2 dimensional by definition.
Once something has passed the edge of the visible universe it is effectively lost to us
Only until we build a bigger telescope.
a bit like when something passes the event horizon of a black hole.
It's not really the same because anything that collides with a black hole will cease to exist. There is no way for anyone with any sort of conceivable detector to observe what no longer exists. Even if the collapsed star's gravity did not stop the photons from exiting it would effectively vanish out of existence.