The queen hides inside the landing gear compartment of the dropship.The inner structures had the "Sulaco" name because it´s his mothership.
The queen lays a undeveloped egg(the big abdome serves to mature them).
The Sulaco sensors array can not detect the egg because it´s hidden inside the dropship fuselage.
The queen dies,the crew go to the cryochambers.
The egg mature,the facehugger feels the presence of potential victims and leaves the egg to attack them.