The door that connects the Science Wing with the tunel checkpoint (the tunnel that gets you to the Crew Quarters) in the Ocean Lab is fully locked, with INF Damage Threshold and INF lockpick dificulty.

I already defeated Walton Simons, that is to say, I already unlocked that door a long time ago when I first got there in route to the Crew Quarters, but now the door is locked and I just can't get past it. I remember I used a code to open that door back then, but the NumPad was in the Science Wing side, not on the Tunnel side. I've checked Simons body to see if he had a key or anything, but all he had were his weapons. Is there something I'm missing?