In Japan I often felt いいえ or 違う is not the best choice, when asked, if I don't carry something with me. Like at the airport security lady asked me, if I there were any forbidden objects in my luggage. I can't recall the question, but it ended in ない？ I felt lost for a second and she tried to help me out with a correct answer and said in a confirming tone ない, and I used her tip and said ない！
I used that couple of times in other situations. Is this okay to say it like that or should I produce a better lengthier sentence, like 何も持っていない?