I think "frozen" in the OP means that rigor mortis has set in so the snake is stiff, not that the temperature is cold enough to freeze water.
If your snake has passed away then you will need a necropsy to determine cause of death and even those can be inconclusive. That said, if his hot side was only 75*F and his cold side was 70*F at most then he could easily have gotten sick and died, or perished because he was unable to digest food and it rotted inside of him.
Since you are not in control of your home's environment I would suggest not getting any exotic pets that require specific temperature and humidity ranges until after you have moved into your own place.