Pretty sure I remember reading some years ago, that like Hospital infections, Most of these problems are caused not by dodgy kitchens, but by dodgy guests.
The most common thing is an employee that's ill/not fully recovered coming into contact with the food, but with a buffet it could just as easily be a guest.
The kitchen can be spotless, doesn't matter if the people handing it are carrying the pathogens.
When I wrote the thread, it was an 'I'm angry at the world because I'm unwell and deserve X, Y, Z' ...now my fever has dropped off for a bit and I'm more rational, I know I'll not do anything. It'll be nothing more than a rubbish story to share. Thank you.
It's probably not worth your time anyway, if you could prove they caused it through malpractice the owner might get barred from operating the business and receive a fine, however I doubt you would receive anything unless you could prove loss of earnings etc.