Usopp might be meek, but at least he wasn't stupid. After a few seconds thought, he opened the door again, grinning a bit too wide as though that canceled out his previous panic attack.

"Hi! Sai! Nice night! Weird intercom message. I guess you got your outfit back too, huh? Ha ha, yeah, I did too, see?" He stepped out into the hallway, hands on his hips as though either showing off his outfit or his sheer manly lack of terror. "Listen, um, about tonight..." This might get awkward. "Some of my crewmates were going downstairs, or going to try to. I don't know if I'm going with them or not yet, but I need to talk to Luffy first."