I am a necromancer. My undead are created using animate dead. As I can only control 4HD per CL, when I go over this limit I must release them, but I get to choose which ones are released. This implies some kind of awareness of the undead you control when you are the creator, whereas using the feat command undead doesn't say how it works in that regard (either you lose control of the oldest, as you choose, or simply unable to use it when full).
So as you are able to choose which undead you release, would you recognize when one of them that you created and still control, is destroyed?