I have a practice of putting the sticker on the fork, only visible by peering directly down from above. I could see someone challenging me on it once, after that, I would expect them to remember, "Oh, I've checked that vehicle already and he's good." I feel for you. I had a scooter stolen from in front of my house about ten years ago, and twenty years before that, someone stole a pickup from right under my nose out front.