Is anything else electrical not working? Cuz it could be the start of your alternator/battery goin, or maybe a blown fuse??? Did you try turning the car all the way (started and all) and then checking the rpm gauge, cuz although u may think it, when just the battery is on the rpm gauge doesnt move even if u hit the gas, its a common misconception.
Maybe i dont know jack shiat, lemme know if this is true.