Are asteroid-mass black holes hiding in the cosmic gamma-ray glow?

There are multiple ways to form black holes. The one most commonly taught in high school physics classes is that they are created from the collapse of a dying star. But there is another class of black holes, known as primordial black holes (PBHs), that could have been created immediately after the Big Bang by matter collapsing in on itself. Or that's the theory, at least. Though long theorized, we've never actually seen one of them, though scientists have suggested that they might accoun...