I think it would be good to encourage everyone with food poisoning to notify a central authority to collect statistics, but blaming a specific restaurant from a single case is dicey at best.
It’s also worth noting that most people expect meat to be the riskiest type of food. In fact, lettuce is much more likely to cause food poisoning.
(Ground beef is indeed more dangerous than solid pieces, but most chain restaurants are pretty careful about their HACCP and are likely to cook it properly. Your average large burger chain won’t serve rare beef patties even upon request.)
About ten years ago one third of the office (50 people out of 150) called in sick, it was pretty clear which meal and which restaurant was the culprit.
Identifying the culprit is certainly easier when you have a whole group of victims.
Reporting food poisoning if it ever happens to you (even if minor) could be the difference between someone else being believed of being shut down.
In secret someone who cares less about your health than anyone you know prepares hundreds of meals a day and if they don't come in because they are sick they lose money. If they don't try to hide mistakes it will cost them. If they don't save the company money by picking up food off the ground or using yesterdays soup as a base for today's soup they are doing a poor job. There are very few ways a customer can prove these mistakes unless they are visible upon receipt. Poor reviews hidden from the public is the only recourse.
As for using leftovers: this will shock you, but a large portion of menu items in even fine establishments use leftover items (that were not served to customers). Soups, stews, curries, etc., generally involve perpetually renewed bases, where the previous days leftovers "seed" the new day's mix. The meats in pastas and other starch-heavy dishes are usually trimmings from entrees in which the meat is the star. Meatloaves in restaurants always use leftover meats from the day before. Nearly all breads in bakeries involve the reuse of the sourdough starter, and indeed the concept of sourdough itself is premised on the reuse of the the dough.
That's not necessarily a bad thing. There is such a thing as a perpetual stew [0] in which a stew is replenished with ingredients over months or even years.
Nothing of what you claim is normal or typical in food service.
Source: I've worked in food service. Everyone takes health, safety, and quality very seriously.
It makes you wonder: did the lawyer call each one of those thousands of people, did anyone get sick but didn't realize it was the burger, time could be an issue too maybe a few lettuce leaves had listeria on them but it only grew to levels after a certain time and temperature.