Its not evolution :lol: You nailed the answer yourself though.
"Also, it is completely nocturnal (ran from a flash light). And is a pretty quick moving bugger..."
Thats why you probably didn't notice it. Mine run for cover when the lights come on. If I look at the glass late at night, there are dozens on it, if not hundreds. As soon as the light comes on, its the mad dash for cover.
They can hitchhike on anything, live rock, corals, etc.. It may have hitched in on a recent coral purchase.