Try typing “missing” (without quotes) in timeline index search field. Or in the event browser search field. You can also create smart collection with “missing” as the search criteria to quickly find what is offline in library. Make sure to type whole word.
Hope that helps
I see this all the time, and not only with audio, but with video as well. It constantly happens to small pieces of video that are not on the primary storyline. Once you zoom out it jumps vertically. Grouping into secondary helps but that is still annoying. 10.0.x then 10.1.x and now 10.2.x.