Well, some photos to ensure they don't make things any worse would be a good idea. It would also have some psychological impact like "hey, this guy means business". Also, ask them to wash it. If they refuse, ask if you can take it for a wash to get a better idea of the extent of damage. And FWIW, any overspray should only be on the side that was facing the house being painted!

Keep in mind that while latex overspray may have dried before hitting the truck, it is a form of plastic and will sort of melt to a surface. But I GUARANTY that it would scrub off with minimal effort. And by the way, alcohol dissolves the stuff.