Airpods just disappeared from settings
Credit to 9to5Mac

To check &amp; update the AirPod firmware, do the following:


Have your AirPods nearby and open the case. The normal status/connectivity window will pop up, but you can swipe that away and look at the ‘About’ screen and scroll all the way the way down.
On the iPhone/iPad, go to Settings -&gt; About.

Open the AirPods case and have them near your phone. 
Tap the new AirPods section in the About menu.

From there, you’ll be able to see detailed information about your AirPods, including the model number, serial number, and hardware version. Your info should be similar to this:


Manufacturer: Apple Inc.
Model Number: A1523
Firmaware Version: 3.5.1
Hardware Version: 1.0.0

If the Firmware Version is not 3.5.1 then you'll need to update them.  Just keep them in their case, plug them in, and next to your iPhone.  The update should happen automatically.  It might take a few hours so it's best to leave them overnight so the update can take place.