I will start by saying i have no experience with this ESC, however after doing a quick spec check in a traxxas forum it says it can handle peak 100 amp, besides 3 s lipo being too much voltage you also state the battery is 20c , now if the battery is less then 5000mah then it cannot deliver the required power that the esc will try to suck out of it, battery should always be able to deliver more then the esc/motor will draw otherwise it can damage the esc, in saying this the most likely scenario is the 12.6 volts have probably toasted your esc, but you never know stranger things have happened, good luck either way.