Question : Hide Terminal Server local drive from Remote App

I am trying to hide the Terminal Server C: drive from RemoteApp users. I have a Group Policy in place that hides the drive when users log onto the Terminal Server.
But this policy doesn't seem to affect users who use the RemoteApp. I use the same Terminal Server, and same user account.
Is there another policy specifially for hiding the drive from RemoteApp users?

Answer : Hide Terminal Server local drive from Remote App

I worked it out-I was using cached credentials to connect to the terminal server.
I had earlier RDPed to the server as the administrator, and it saved these credentials. So each time I opened the remote app, it was using the admin credentials
My GPO isn't applied to the admin account, so the C: drive was visible.
To clear the cached credentials, I went to RDP. There's an option to 'delete' saved credentials here.