So I got worried and eventually went outside and started calling out "Dev! Dev!"
I heard mewling in response.. and I went in to tell Peter I heard mewling.. at that time a neighbour of Peter's asked me: "Are you looking for a black cat? He's up there."
Dev is on the roof. Of the 2 storey apartment building. He's stuck there. We just tried to get him out with a basket and a chair.. with Peter lifting the basket on the edge of the 2nd storey fence, and me grabbing hold to Peter. He almost got into the basket too..
Finally we gave up. 311 said that animal control won't come for cats.
Ok.. we're going to try again.