Is that the theory where the Queen is still capable of producing premature offspring without the need for the egg sac? The egg sac is only an incubator for growing the eggs. Yeah. I subscribe to the that theory but have my own spin on it.
If you accept the The Queen is still capable of creating offspring, then all you have to do is connect that offspring to the egg on the ceiling in the hypersleep room. It's not that hard to do, actually. As we can't know everything about the Queen then there's plenty of leeway to do so.
Here's my take on the entire sequence regarding getting that egg in place. It's a lengthy read, but it's all there...
The Queen drops a few proto face huggers on to the deck from the remains of the part of its body that was attached to the eggsac. These protofacehuggers, as speculation permits, are only partially formed. To become a complete facehugger, they need the egg; and as the eggsac is not present they lack the necessary environment to become fully formed via conventional/accepted means.
Let's just say that these incomplete facehuggers are capable of one thing during this very vulnerable stage - SURVIVAL. They lack the grasping spindly legs but their tail and other functionality is present. They are the most rudimentary stage of the facehugger that is capable of survival. The strong tail is capable on its own to make the proto facehugger (earlier in this thread I referred to this stage as a 'spore' but it was clearly misunderstood - so I'm spelling the concept out more clearly here).
These are dropped during the fight between Ripley and the Queen. As to whether they get noticed by anyone? Let's just say they don't for the sake of getting an explanation happening here.
Anyway the proto facehuggers are still highly mobile and IMMEDIATELY use their strong tails to seek cover. Blink and you miss it move. Just think of the spring loaded tail suddenly propelling the spore and you can imagine how easier it would be to miss during that scene which was loaded with commotion, anyway.
They find cover, migrate around the ship and by the time Ripley's 2 minute confrontation with the Queen is over, they've already found safe cover.
Ripley and co. then hit the sack, and these proto facehuggers are still loose on the ship. Hell, maybe even Bishop knows they are there. He seems to anyway as indicated by dialogue in the third movie.
So, they go to sleep and these proto facehuggers are free roaming around the ship and need a place to 'roost'. The ship powers down (I've outlined this process above somewhere above as to why this is necessary.) Gravity is reduced to 10, maybe 20%. The reduced gravity affords (at least one) of the proto facehuggers even greater mobility and it attaches itself to the ceiling in the hypersleep pod chamber. It nestles there because it knows that potential hosts are resting nearby. At this stage, it's still essentially just a tail attached to some organs in a ball bag, needing a safe place to mature.
Now, it needs to grow. So it sends out tendrils and it roots itself in place using the very ceiling as a place to grow an egg around it so it can mature fully inside. It keeps increasing in size on the ceiling while it draws nutrients from the conduits, pipes and airlines that would be in abundance in this location to service the hypersleep pods. Eventually, it grows into a full size egg, hanging on the ceiling.
Now, we know that the eggs are opened when someone else approaches them but no one is going to do so while they are all in hypersleep. The nature of the inverted egg actually provides us with the triggering of the now matured facehugger. Even at 10%, gravity would be adequate to disturb the growing contents of the egg(s). It opens when the mass is pressing against the inside of the upside down flaps and the egg has no choice but to open and release the now fully formed facehugger onto the floor right next the occupied hypersleep pods.
So, yes. It can be explained. Is it canon? No. But without such speculations, we are at a loss how this egg came to be in this location. I acknowledge that this theory may not be fully water tight - but there are other elements of these movies that lack credibility, too (artificial gravity for one, distance between planets is another, keep looking and you'll find all the debates strewn across these forums for more.) There's always a threshold where we must accept that somehow this can be explained, though.
Of course, some people DON'T WANT IT EXPLAINED for the simple reason it validates 'ALIEN 3's existence even more. Well, I got News for you. The movie has been around for nigh on a Quarter of a Century. It's time to accept that.
-Windebieste.