How can I find my missing AirPod piece

Hello,

If your AirPods are out of Bluetooth range, out of charge, or in the case with the cover closed, Find My won't give a current location. You just have to find them manually by looking for them. However, Find My may list the most recent location where they were last connected.

See this for more detail:

If your AirPods are lost

Good luck.

ask Siri “find my airpods” they will emit sound if close