Based on my experience with recruiting at McKinsey, events are a great place to network with the consultants at the firm. We were asked to write down the names of candidates that we found promising or sometimes even to pitch the firm to candidates that were already considered strong. I would encourage you to make a strong effort talking to people and also try to speak to some of the more senior people at the event, their recommendations matter a lot.
It is likely that if you connect with the consultants there that they will inform HR and any recruiting leads about you, which gives you a better shot at being invited back. You would still have to meet all of the other criteria such as being from a top school, having a strong GPA etc.
Hope that helps,