Are you high enough level for the next quest? The attendant will actually not let you back there again to see Cid until you're high enough level to actually do the next quest. I noticed this specifically during the Garuda phase of the storyline, I was one level short of being able to do her.. so I left the dock. To my dismay I noticed there was no way to get back to Cid.. Nonetheless, I knew it didn't matter since I wasn't high enough to continue anyway.. soon as I leveled though, the attendant happily let me back there as you'd expect.