Has to be crap. The sound of an upright 47 at idle is significantly different to the sound of one rolling down a hill, a fact I can verify from personal experience. Unless our hero was in the habit of wandering 2 kilometres away to find a suitable tree to fertilise or the Berlin Philharmonic was practising the 1812 Overture in the next valley, there is no chance this mishap could go unnnoticed even with other 47s buzzing around overhead. IMHO of course...........