If there is no white lines on the road the lorry shouldn't be using it (law statement not mine) so the lorry is responsible even if they weren't. Get after the company owning the lorry.
I'd love to know were this came from. I've been through the highway code many times and endured countless hours of classroom modules for driving lorries and this has never been mentioned. So I'd be pretty confident in saying that its bollocks tbh.
The company won't give a shlt about your wing mirror.
The driver won't give a shlt about your wing mirror.
The police won't give a shlt about your wing mirror.
It's unfortunate, but apart from a face to face appeal with the transport manager or the owner, both of whom will probably ignore you at every opportunity, I don't think your mum will have much luck. Bad mouthing them on Facebook probably won't do much in your favour either.
Just look at jimcupra and that tw@t on here trying to get him sacked. Nothing happened, no one cares.