It's a long shot, but if I was you, I'd be waiting outside for canine culprit plus feral owner with cattle prod in hand......see owner let dog pee on your bike..I mean, WHO or WHAT kind of feral allows their dog to pee on someone else's property? Maybe they are jealous you have a flash bike? Anyway, said dog pees on your bike, then switch the electric prod up behind its tail. You might get a bit of loose stools from the dog but I doubt it would dare come back again to finish its deed.
If the owner insists, you could use it on them.