I think there was something in there that said they had X amount of minutes after you checked out to call you back if your window is still good. Might have to be those irregular ops. If they claim that I would make sure your union has been notified of the irregular ops.
I also thought you could be released, but if you still had time on your window open, that you were susceptible to another 90 minute call out. Or is that a double DSL?