This is most likely a glitch. Normally, TurboTax will provide a list of documents that require mailing. If your list is blank, then there was probably a system error.
You can print your return worksheets which would indicate which forms might be required to be mailed to the IRS. Also, if forms are missing, the IRS will notify you if additional information is required.
Here is how to print/view worksheets:
Go to Tax Home.
Select the year you have just filed.
Click on Add another state.
You should see Print Center on the left navigation bar.
You can now print all kind of worksheets and forms.