[@athanshadow] I'm not sure when that will be. The PCs are currently heading inside the wall, which nobody really does except in emergency (and there's never really an emergency, so basically never).

How about this? Ezra is probably standing on top of the wall but a bit far away from where the others were. He may or may not notice the other PCs, but he will definitely notice that everyone around him and in the city has turned to stone and there's an army of Grit flying/climbing the wall toward him. There happens to be a trap door near where he's standing that leads inside the wall itself, for emergencies. So then he can meet the PCs inside the wall, which is where they're going now.

Simplest solution I can think of right now. :)