Not only that, but food poisoning usually kicks in at least 8-12 hours afterwards if not a day or two later. It's very easy to assume that it was the previous place that you ate at when it was probably a few meals before that. Usually chains are pretty good at controlling for food poisoning and the ones that aren't end up making the news like Chipotle.
I went to a dinner party at a friend's in Detroit on a Friday and was horribly ill starting later in the evening running through to Sunday night (yes, I got better just in time to head back to work).
Another friend who went to the party and then promptly got on a plane to the West, I figured the poor guy went through [censored] on that flight and probably made other passengers sick. He was heading for a conjugal visit with a girlfriend (he had several) and I assumed that all went out the window.
Talked to the host on Monday and he swore that everybody in his family was OK...the guy from the plane showed up and said his trip went so well that he barely went outside. I felt terrible about effectively accusing a guy who had invited me to a party of making me sick.
I traced my illness down to a tabbouleh salad from our building's cafeteria, the owner told me that they had a new worker who had not been handling food properly and had already been let go. He offered to pay my medical expenses and I told him I didn't have any, just the lost weekend. The guy made fantastic food and I had no qualms about continuing to eat there when he told me that he had addressed the issue...he had tossed a lot of food over the weekend. We used to have long talks about politics and life in general, he had been expelled from his home but was very grateful for being able to relocate to the US and build a new life here. I think he made good coin from his place because all of his food was just unusually good, incredible to find such quality in a workplace cafeteria.