When something like this happened to me it was a short in my power locks that simulated someone holding the button down. It took 3 days for this to drain the battery though.

If something is draining your battery you can take your fuses out one by one and use a multimeter to see which circuit is drawing current when the car is off. Just make sure that the current in the circuit is less then what the multimeter is rated for or you will end up burning out your multimeter.