I am sitting in CMH waiting for my flight, I'll watch the screen and report back. Even if you have sequence # 110 or something you could still get an A in a ligitmate manner. If an A canceles or un-checkin then an A opens up. So if your the lucky person that checks in after someone un-checksin you have an A. Anyway in short you would probably get away with it, however this comes down to the risk v. reward and is it really worth the risk? Also on a side note your not required to show ID on a domestic flight so when they go back through the you could just say you don't have ID.