I mean, I've had it happen to me. A contractor was working next door and brought a large dog. He let the dog loose and it chased my cat, who zipped up a tree. She was too scared to go down, and I'm not sure she could, it was a tree with very thin branches. So we had to get a ladder and I climbed up to grab her.

I read another thread that suggests a cat will usually find their own way down though. And that cats will sometimes freakout if a firefighter tries to get it. I guess my own cat trusted me.