Not that I would ever be so devious as to suggest social engineering, but you can often find ops-related local telephone numbers on the wall behind where the jetbridge "driver" stands near the airplane end of the jetbridge. (This is not AA-specific; have noticed this at many airports and airlines, and I'm sure many others have as well.) Though I've never seen the ticket counter number listed, if you had some legitimate need to get the ticket counter number, I'm sure you could get the number by calling one of those local numbers. But again, as others have said, it's hard to conceive of a scenario in which you couldn't get your business done by calling the 800 number.