Did you have the checkbox "Submit when Finish" selected, and did you accidentally click on the "Finish" button twice?
In 2.1.0 Community, if this checkbox is selected and you click Finish, the item will get promoted to Staging. Hence you would see the item in the admin sandbox, staging, and bob's workarea without seeing it in your modified items list.
There were some issues we had to work around with JSF to better handle double-clicks. Essentially, the first click actually takes the generated XML in your preview layer in your sandbox and flattens into your user sandbox. If you double-click, there's actually no item left your preview layer to flatten - hence you may have gotten a NullPoint. Those issues should all be fixed with 2.1.0 Enterprise.
If you are not evaluating either 2.1.0 Community or 2.1.0 Enterprise, I highly recommend it. Let us know if you've further questions.
Kevin