I'm not sure how potential truffle dog thieves would be able to tell that a dog is good at finding truffles during the 364 days a year where the dog is not sear

I'm not sure how potential truffle dog thieves would be able to tell that a dog is good at finding truffles during the 364 days a year where the dog is not searching for truffles. Or how they would steal the dog while the owner is walking around with it in the forest during the 1 day a year where they are searching for truffles.