the second i got it home, i would have been ripping and tearing it apart to diagnose what happened. i wouldnt be able to sleep until i got to the bottom of it. asking vague questions like this will only get you 1000 possible and probably wrong answers. start with a simple process of elimination. grab the coupler and see if it turns over by hand. if it does, then its not froze up. if it cranks over do a compression test. if it dont crank over, determine if its a battery cable, starter solenoid , starter , bendix or the flywheel fell off.