I suppose it would be too much trouble to let us know whether it runs off an electrical cord or a battery. "Accidentally left it on over night" could mean it was left on the charger or the drill motor ran all night.
A drill is simply a reversible electric motor with a gear system and a switch bundled so you can hold it in your hand. If you check the voltage to the motor with the switch turned on, and there is voltage there, the motor's bad. Other wise, check it back to the outlet or charger at both sides of the switch, and the outlet to see where the voltage is lost.
If you have no experience at working with electricity I would suggest you enlist the help of someone who does.
If you need to contact the manufacturer:
https://www.ryobitools.com/contact_us/new