You are most likely running TFS update 3 which changed the back-end of TFS to create work items for both the Test Plan and Test Suites now. There is something odd going on in your project, it may be that you have not "enabled" the features on the project so those things are done behind the scene.
To verify this, go the TFS portal and click on the little gear in the right hand corner, then click the control panel link (up top left) and select the project you are working under and finally select Manage the project administration page and click the overview tab. Is there an "enable features" button there?
If you go the home page of you project and click the little question mark on the top right corner and select about, what version do you have there?