Hi Matt,
We had a similar situation recently where our K-12 admins wanted to know what students were using/viewing Etherpads and what the addresses of the Etherpads were. Since there is/was no administration tools for Etherpad, this presented a unique problem.
What we came up with was a python script to crawl through all Student users' page views for the last 90 days looking for any page view with 'etherpad' in the name. We used this call to retrieve them:
GET /api/v1/users/:user_id/page_views
This netted us about 10 different etherpads we were unaware of and mostly answered the question.
Now that we're involved in the Hosted Data Beta program, we're able to look at page views from around 1 year ago and see etherpads visited since then.
Hopefully that sheds some light on this issue.