So as it was working ok it could be the servo reverse switch on the tx has been set.
its quite easy for a begginer to think it is the off switch.
so you do this at the end of a run and when you turn on next time the car is going crazy so you try and set the esc with the tx in reverse so it means you will never get it right.
You can download the manual from
www.kyosho.com and check out the esc set up info.