I feel your pain. My trainer did the same thing yesterday. I had made two beatiful flights earlier at a different field. Then went out to another field. Was flying around fine, having a really good flight, went to turn base for some touch and goes, and it just rolled into the wind and buried itself. My first though was that I got shot down, but i also considered that going downwind, a gust might have stalled the right wing. But as it was falling I pulled the throttle back and got no response. Rx battery was fine under load, Tx battery was still good, I was still within range. It's just one of mysteries that will never be solved.