Thanks for posting here in the Google Nest Community.
This is really an unfortunate event. Once you discover that your Nest Hub has been stolen, immediately report the theft to your local police so that they can document it and tell you what to do next. At the moment the feature to track it down is not supported, but it will not work unless it is connected to the same network that it was setup or a factory reset was done which puts it back to its factory setting.
Hope this helps.