..cant you just let it run out of battery
No, he needs to put it into DFU mode, which is required for jailbreaking, and which can only be done with the use of both the sleep/power button and the home button.
@OP: Unfortunately I don't think there's anything you can do. Is the warranty on your device still valid? If so, you can get it repaired at the Apple Store, possibly for a price.