I think this may be the same hub I keep trying to hide. I've done the same thing - I've unfollowed it, and hidden it about four times - unfortunately, it always appears on my phone when I look there.
I think if it's in a topic you follow, even if you don't follow the hub itself, it may pop up. I had a similar problem with one from a hubber who had trolled one of my hubs, then wrote a series of hubs that re-iterated his answer (the one he had provided on my own hub when trolling) - because it was in a subject I follow (which, unfortunately so is the one I think we are trying to sort!) - it disappeared when no one replied, and when he got banned!
Perhaps asking in the Forums - technical ones maybe, and HP staff may be able to help. I'll try a few things and see if that changes anything. Good luck!