I came back from a short weekend vacation to find my return pump had failed!! The impeller appeared to have been encrusted, likely by calcium build up. I do regularly clean the main pump, but looks like it just hadn't been done soon enough. Luckily it had not been out of commission for very long by the look of it, and I had a smaller pump the get things back up and running while I had a new one overnighted. Lesson of the day is its not a bad idea to keep a back up pump in case of failure.

