An idea we're toying with is wing covers. That way the ice will (hopefully) form on the covers rather than the wing. Also if we have them in a dark colour there'll be solar gain to warm everything up that much quicker if the sun comes out. Should also make washing the plane easier. We already have a cover over the cowl, screen and windows and never get ice forming on them.
FFF
Possibly what happened is this:-
The air was super-cooled. It was cold enough for the moisture to condense out but there was nothing for the ice crystals to grow on. You provided it.
Mike