What does the note on the coffee bar counter mean?

The bold capital letters should be clear enough.

But who sent it? Someone from cabin 3001.

The odd numbered cabins seem to start from 3003. Right before 3003 there is... the cargo bay.

And what was Evan's surname again?

Go check on Clarisse and Evan. They need your help.

With the door locked and no override mechanism, you may need the help of someone who can move around the ship and knows it intimately.

Yes, the ever helpful steward.

Now where is a working access panel when you need it?