how is the rotor connected to the wheel hub? on 2001 Lexus IS300

I was rotating tires and went to put tire back on, when i did the rotor pulled out and felt like the only thing holding it back was the caliper. is there suppose to be play in the rotor like that?

Asked by for the 2001 Lexus IS300
the rotors are supposed to have play in them
thanks! I was a little worried there for a min. Ok, another question. I am smelling anti freeze when i get home after a short drive to the store. I pop the hood and there is a small amount of antifreeze beaded up at the very top of the radiator along the foam shim in between the radiator and the frame where the screw goes to hold the air scoop that comes on the IS300. white splatter is on the cover of the pulley area. and anti freeze was dripping from the under side of the hood itself where the rubber seal is along the hood. Whats going on here?