i believe the last bus leaves at 9:30 just so they get the last of the stragglers. after that your pretty much on your own.
you may want to think about getting a day room at the hyatt at the airport. we found this a blessing when we had a late flight out. they have a swimming pool , which proved to be handy. you have a room to relax in, take a shower, have a nap. you also have the run of the airport as it is right their so some shopping and dinning at your fingertips. it was perfect for us, maybe not for you but a thought.