Good luck with that. I've found gate agents either to not exist, or the 1-2 of them get completely overwhelemed as an entire flight needs to rebook. Passengers who were only connecting to another final destination add further complexity. Obviously the OP took a risk that the airline wouldn't refund his new flight but the alternative of waiting in a giant line or finding a non-existent agent from a budget carrier to hopefully rebook you isn't great either.