First of all Good Job Sherman. I'm sure it must have been an excellent exhibition. Secondly, I recently had a friend go through the exact same experience. Our sensei asked him to demonstrate several techiques for the class and in the process be "very attentive to his body". As he went though each technique he became more and more confident of his technique and at the end we all congraduated him on his wonderful nage and uke waza. In all I believe what your sensei may have done was see you be confident enough to handle this type of situation, where in fact you would be surprised as to the abruptness of the test. Yet, at the same time, show enough composure to execute your technique to the best of your ability. That in itself is a part of Aikido, to expect the unexpected, even when it seems so familiar, "Expect nothing. Be ready for anything." But, as you showed, the ability to stay calm, react, and most importantly, to adjust, made your test so memorable and emotional. Best to you on your next test.