If it was towed...Does the rear turn normally? If the rear does..Does the trans turn by hand in nuetral? I'm inclined to say the trans broke, and the rear just let go because something had to give. If the yoke breaks (and I've broken about 10) the engine freewheels, but there is no stress on the trans other than the shaft spinning around, and that might break a tail housing (one of mine did) but shouldnt hurt anything else. Tremecs may be a different animal. But I would be very careful to check everything out.