There are two types of liability coverage a restaurant like this would have. The first is general liability. The second is negligence
. General liability usually has a medical payments coverage portion of the policy which will pay a particular amount for anyone who is injured on their property. You have very strong grounds to get this part of the coverage. The problem, is that this coverage is usually only around $5,000. The second type of coverage is for negligence. Negligence occurs if the restaurant failed to exercise reasonable care that a reasonable person would exercise in their place. This is much harder to prove, but not impossible. For example, if anyone else was sick at the restaurant, the chances of you succeeding on a claim go up exponentially. This is because if only you were sick, they can argue that 1) you got sick somewhere else, and 2) even if you got sick there, it was a freak occurrence and there was nothing they could have done. If someone else also got sick, then it would 1) prove you got sick there, and 2) give a strong argument that the food must have been mishandled. Not just one piece, or your portion, but the entire thing was left out to long, or shipped improperly, or there was some act which was below the standard of care.
As for what to do now, you need to try to 1) contact a personal injury attorney in your area immediately. Not having an attorney in a case like this will cause the insurance company to walk all over you, prolong everything, and cause your life to be miserable. And 2) look up any and all information you can about this restaurant and hopefully find some other person out there who also got sick that day. If you are really lucky, you may even end up with multiple people.
If you decide to hire an attorney, a great resource is www.Martindale.com. This is a nationwide directory that is useful in finding highly qualified legal specialists in various fields of law. The lawyers in Martindale are not selected because they paid to be included, but rather because they have been rated by other attorneys as qualified experts in their field. Consider consulting with two or three different attorneys prior to selecting the one you feel most comfortable with. In a case like yours, an attorney will likely take your case on contingency, which means that you will owe nothing out of pocket.
Please do not hesitate to let me know if you have any questions or concerns regarding the above and I will be more than happy to assist you further.
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Have a wonderful rest of your day, and good luck!