Finding stolen AirPods
AirPods only note their location in Find My iPhone when they pair with your device. They have no built in location tracker and no way to communicate to the internet except through your paired iPhone or iPad or Apple Watch. 

The person may have reset them, but even if they didn't you wouldn't get any location updates unless the thief walked by and remained in range of your device long enough for the AirPods to pair. 

The reset doesn't change the identity of the bluetooth module so that may have nothing to do with locating them, either.