May be you missed it, but the name is there in the alert. One way to see the alert again is to right click avast! icon in the task bar and choose " Show last popup message ". This only works if no other popup message has come up after the fact or if you have not rebooted the system yet.
The last program you allowed would be last in the list in EXCLUSIONS > Hardened mode. You should high light it and delete it.