First of, I am sorry to hear about the possible food poisoning!
Been there, done that, and it sucks big time!
Most likely happened due to someone not properly washing their hands!
Then I have a similar story... or two about the unsafe handling of fast food.
At a Taco Bell across from our place, it was not mandatory to wear gloves while preparing the food, and you know they touch everything with their fingers, then come and tender the cash, quickly run some water over their hands, kind of wipe it on a cloth that sits next to the food prep area (and is also used to wipe away access food or sauces) and back to preparing the next big bell meal. I've seen it numerous times and we tried to tell them to wear gloves before touching anything that is being prepared, but they either give you dirty looks or act all gumpy. At some point a friend of mine called the local headquarters so often and complained that he will contact BBB and Health Department that it is now mandatory to wear gloves and that they have extra people to run the registers! YAY a win on that, but their food still gives you the runs...
Another story at Jack In The Box-
We went through the drive through, paid and waited for our order, as the person working there, prepared our Oreo Cookie Shake, filled the cup way too much so that when she tried to put on the lid, the contents started to come down the cup all the way around... She took of the lid again, LICKED her fingers that had shake on it and touched the rim of the cup to put it down before trying to fix the same lid on it again!!!
At that point my wife asked for the manager right away, who acted like this was no big deal! We asked for our money back, drove home and called Corporate, after about 15 minutes being send back and forth, we finally got through to someone in charge, who told us that they will be checking up on this (yeah right) and then offered us free meal tickets!!!