You ask the crew member where your friend went. You keep your tone light, like you are just making conversation.
The crew member smiles right away, but it does not reach their eyes. They say your friend had to step away for a moment, and then they ask, very casually, if you are traveling alone.
When you look past them, you notice a door at the end of the dining area. It is marked STAFF ONLY. Someone is standing near it, not really blocking it, but not moving either.