Unfortunately, if someone finds it and connects it to their iPad, the Pencil Pro doesn’t have any ownership-locking like AirPods or iPhones do. That means they can pair it to their iPad without any alerts to you—and it won’t notify you via Find My when it's paired to another device. There’s no “stolen” or “lost” mode that gets activated to notify you or block the new user.
Find My support for the Pencil Pro is not quite the same as how AirTags or iPhones work. If the battery is dead, the Pencil won't emit a signal, so you won't be able to track its current location via the Find My network until it’s powered on again. However, Find My will still show you its last known location while it still had power, which might be helpful for retracing your steps.
Your best bet is to keep an eye on the Find My app for any sign of it popping back online—just in case someone charges it near any Apple device and it gets picked up on the Find My network again.