On the Mothership Zeta DLC, after you blow up the other spacecraft, go to the teleporter that all the others came from. You will end up in the Engineering core again. Go to the corridor and walk slowly, looking down at the floor. NOTE: May need pip-boy light on!

have fun with a second chinese commando hat <img src="http://i.neoseeker.com/d/icons/smile.gif" border=0 vspace=2 alt="" />