I'm glad you were able to find the culprit before you wasted more spurs. I'm not a Revo expert but I'm sure one of the Revo veterans here can provide you the info you need. Even on my TMaxx the motor mount was one of the first thing I replaced.
Did it strip while you were running your Revo or did it strip while it was just idling. If you were running it the time you stripped it, its possible some kind of debris got into it and caused it to strip. Also possible if you did a big jump and landed on one side first it might have been...