smokin ESC question.

I was driving my stock e maxx the other day in the sand with paddle tires installed. This is the second time I have had it in the sand, the first time it sounded like sand got into the motors. So this time I though i'd try to sand proof the motors. This could have been my mistake. I put a nylon stocking over the motors to keep the sand out. It ran good for about 10 minutes or so then it shut down. I took the body off and the ESC was smoking. I unplugged the batteries as fast as I could thinking that would help.

Its an e-maxx 3905. I wasn't running it all out for 10 minutes, just regular driving, throughing some sand around.

Is the speed controller fried?