Can't get back to do tasks in the elevator

Hi I'm fairly near the beginning, in the bell tower, where I got stuck looking for the second fang.
Peeked at the strategy guide and I should have done some things in the elevator (Like find the fang)...only I was in too much hurry to see where it took me
but now I go straight from the bell tower downstairs room, to Saint Mark's Square, by-passing the lift and I can't access it from either side.
Am I doing something wrong or will I have to start all over again?

Thanks