error seen by user when 'Rejecting replayed message ID'?

[Paul Henson]

I'm still trying to sort out a problem with a client whose application
is getting NoSuchFlow errors sporadically when trying to authenticate.
The operator of the idp involved is pointing to some 'Rejecting replayed
message ID' logs around the same time as the issue occurred. I didn't
think that would return the same "maybe you hit the back button" error
page as the application is receiving, but I don't know that I've ever
experienced the replay error myself.

What would one expect to see in a browser as far as an error message
when the idp thinks it has detected a replayed message and aborts the
authentication?

Thanks much...