It was probably a spare warrior they had onboard since that's what happens in basically every Alien 3 script except for the final ones.
Just hid somewhere with a couple eggs (or three? it implies one of the facehugger's died trying to get in, which allows Newt's tube to get filled with fluid) it managed to salvage tailing the Queen, because they plan ahead in case of natural disasters and earthquakes, and nuclear explosions, and greased them near the cryo deck before eventually dying off somewhere. Problem solved.
What I want to know is, what happened to the Sulaco since its just floating there with easily retrievable alien material on it. They were going to film an EEV hurling backwards into it and exploding, but neither cut has that. Is that canon? Or did it get sucked into Fury 161's gravity and crash land somewhere. Or was the fire really that bad, didn't even think of the fire.
So I guess, the only logical explanation for all of this that's shown is a leftover crabby alien lugged some eggs, hid, cried about how mom is gone, shrugged and said "it's a living", starved to death, or was surprised that a facehugger +cracked glass = acid. Crossed his heart, said "dios mio" and died in the resulting explosion. That's all I've got.
