Sharp as a knife

I will spare you the pain of my experiences with US airport security during our trip. I will, however, share what I thought was an impressive piece of detective work. As we rolled Luc's hand luggage through the security machine, the conveyor belt stopped abruptly while a couple of inspectors took a closer look. After a few seconds of examining at the screen, a rather fierce looking officer came over and asked "Do you have a knife in the bag?". I could sense my fellow passengers eyes drilling a hole into my back. I wracked my brains wondering whether I had inadvertently slipped a carving knife into Luc's luggage before confidently answering "no". Without a moment's hesitation, he asked "In that case, is there a toy limousine in there?".