Thanks for confirming. I tried finding it in T&Cs but there's nothing.
I've emailed Hyatt. Hopefully they do the right thing. I judge companies not on the mistakes they make but how they deal with them. This was a huge and stressful mistake, granted, so unless they compensate me fairly I'm washing my hands of them altogether. This was my first stay in many years at a Hyatt and might be the last.