Don't worry, I found it; right after you open the door after killing all the Aliens at the beginning of the level, go right up the stairs after exiting the hallway. Once you reach the top of the stairs, look right and you should see a tunnel that is elevated; you need to pounce off some debris nearby in order to get the egg at the end of the tunnel. The secret room vision that the Berserker Alien has won't help you here; you have to find this place on your own (took about 3 tries to find it, myself).