Once you’ve renamed the notebook, you won’t be able to open it from the “Work in Browser” link anymore. But you can use the “Help → Lab Help → Get Latest Version” to get a clean copy of the notebook. Once you’ve done that, you can then open and rename your original. See the FAQ Thread for more detailed instructions.
And, no, we can’t restart it for you. The mentors do not have the magic powers to see anyone else’s assignments or accounts.