Sorry to hear that, Ken. Happened to a couple of friends over here, too. I remember one guy that had his plane accelerating on his own at least twice in my presence... We bought a small wooden fence, about 2x2m, for his birthday last year! ).
If the other guy is insured (either from the local aeromodelling authority or private) maybe this can be put under "accident" and have the insurance pay for the damage. Worth a try.
Regards,
Fabrizio