Airpods Don’t Show up on Find My iPhone

I recently misplaced my AirPods, which is a typical occurrence for me, in which case I just use the Find My iPhone app. But this time, I opened it to see that it not only wasn’t detecting my AirPods’ location, it didn’t even have it registered as a device of mine anymore. It’s like I never had them. How is this possible? If someone took it, and registered them to their own iPhone, does it boot it off my iCloud? Is there anything that can be done to remedy this? I’m fairly certain they are dead at this point, so if I were to be able to find out it’s last known location, it would be immensely helpful to know whether to continue scouring my own house or give up.