When you stare long enough into the mini-map, is stares back.
That happens a lot if you open other fullscreen applications and then tab out to swich back, or sometimes when you minimize Cataclysm DDA.
Did you do something like this?
Nope, the only window I had opened since turning on the computer was the game launcher an the game itself. In no way did I tab out or minimize the game until I noticed this on the minimap then I did the stuff you mentioned.