What are they going to say, "hey we didnt follow the contract, why didn't you know about this trip in which you weren't properly notified?"

I've had this happen a few times over the years. Eventually they call (usually when you miss sign in) and just ask what time you can make it and that's the end of it. It's not different than when they try to assign you a trip after you haven't been properly notified of 30 hours rest. You tell them you don't have legal rest, the push back, check the tapes and then take the trip off your line.