That's hilarious! I picture them announcing over the loudspeaker "this person actually has real food with them!" and a big, Far-Side style red arrow suddenly pointing at your head as everyone turns to look at you!
Hooray for planning ahead!
A co-worker overheard me talking about Paleo and reeled off a hundred "can you eat...." questions at me. Afterwards, she came out with this beauty:
"I think my son is Paleo, all he eats is hamburger helper"!!!