Maybe a recommend from someone not signed in, I read something about Medium allowing people to recommend without it being linked to a profile — although I am not sure if that is possible yet.
If it’s a bug, it’s effecting me too. I only saw you and Heath, yet 3 hearts.
The only other thing I can think of is someone who has blocked both of us recommended it and we can’t see it. Which is a little creepy when you think about it, so I rather not.