FormsAuthenticationTicket Null After Authentication Timeout?

I'm implementing an authentication timeout detection mechanism per a previous question and answer of mine here. I've implemented an HTTP module that uses the AuthenticateRequest event to run code to capture whether the authentication period has expired. The code to do this is below:

public class AuthenticationModule : IHttpModule
{
#region IHttpModule Members
void IHttpModule.Dispose() { }
void IHttpModule.Init(HttpApplication application)

[Code]....


The problem is that, once the authentication period has expired (I set it to 1 min to test), there is no longer a forms cookie (see comment in code). This means that the authentication cookie will be null, and I won't make it past the null check in my code. But there's a convenient "Expired" property for a FormsAuthenticationTicket that I feel like I should be checking to see if the period is expired. But how do I get that far if the cookie is no longer there? Is it reasonable to assume the authentication period has expired if there's no longer a forms cookie?