Team coding is configured correctly and integrates with a 3rd party VCS. Checking out/in using the toolbar works OK. However:
4. Close the editor tab
Toad checks out the object successfully, and it appears that the item has checked in successfully, when, in fact, an 'undo checkout' has actually occurred. No revision is created in the repository and the database object reverts to a state prior to check-out.
WORKAROUND
Ensure that the object is manually checked in using the button on the Team Coding toolbar, before closing the Editor tab.
STATUS
Issue fixed in version 13.0. The latest release can be downloaded here