Hi Phil,
What version of Windchill are you using? Some of these features are in 10.1 (possibly in 10.0, I am not certain). If you open the Workspace in the Creo embedded browser, at the very top it should say Primary Active Workspace: {some workspace name}, and then "-Pick an Action-". From there you can choose to apply a previous frame.
Even then, it needed to have been enabled. By default it is not, so you might still be out of luck.
For more information I would suggest searching "About Workspace Frames" in the Windchill Help Center.
Micah