They do tape the auditions so when all auditions are wrapped, they can go back through the tape and notes to look at the ones they marked down as a possible "yes".
They told everyone that was waiting in line that nobody would find out the day of auditions. Our case was different as they kind of let the cat out-of-the-bag that day for us. I have a feeling that everyone that was picked last year had a pretty good idea when they left that day. We were in the audition room for at least 15 minutes. We had a very engaging conversation which led us to believe we were in. Most people I saw in Chicago were held to the 2 minute pitch time. If the judges are interested they will give you the time you need. They only put a 2 minute time limit on it so they aren't in each city for a week, if you know what I mean.