Wow, that's kinda nutty. It's my opinion that if you don't know for certain your dog is going to come back to you when called, that it shouldn't be off the leash in public areas at all. Especially if they're not even your own dogs!
Crazy that they chased you that far. Gotta wonder if the dog-walker even found them again.
Maybe some pepper/bear spray might be a solution? I'd rather give a dog some sore eyes than sink a knife into it, for sure.