You don't need to be working in the project to have ownership of Elements on the Central. You should be relinquishing ownership of elements at the end of each session, that will help to avoid these situations.
We are releasing a White Paper on Revit Platform Best Practiccs to all Subsctiption Customers today, and that will provide a lot more information on Worksharing. Check out my blog for a post on that later today.
Cheers,
Kyle B
Revit MEP Product Manager
inside-the-system.typepad.com
Kyle Bernhardt
Director
Building Design Strategy
Autodesk, Inc.