Forum:Head of state

I encountered bug while playing the head of state quest. After telling Hannibla Hamlin, that the memorial site was clear, he asked me to meet him at the memorial site, but when I travelled there, there were no-one. I tried waiting, doing something else, but Hannibal and the rest of the slaves seems to have disappeared, because they were not in the temple of the union either.

If anyone has encountere this bug, please advise.