The middle part of an instance ID is the first part of the owning model’s UUID. As an admin you can list all of the models on a controller using the juju models command. Combining that with a simple filter would allow one to get the model information for a particular instance. For example in your case you could run:
That command would give you the model summary for the model running the instance.
A couple of things to note:
This will only work for “superuser” level users on the controller. Normal users can only see their own models.
JIMM doesn’t support “superuser” level users in the same way as a normal juju controller so it’s not possible to run this check across the whole system, but rather one has to scan each juju controller one at a time.
You may also be able to check the /var/log/juju/audit.log on the controller model machines to determine the user who executed the ‘add-model’ command for that particular model.