Things to consider

Are you injured? If you are, you may have a case of implied warranty of merchantability. UCC 2-314 states that commerical goods must be fit or ordainry purposes. Most courts today are using consumer expectation test in which a rubber band is certainly beyond expectation of any reasonably prudent consumder. Minority courts use foreign/natural test, in which a rubber band is certainly not natural to lobster.

You will also have a case of negligence that you need to prove that the restaurant fell below due standard of care when preparing the lobster. Either way you have to prove damage. A pure emotional distress may be recoverable. In 1987 in Maryland, Yong Cha Hong dined out in a fired chicken restaurant, Roy Rogers, owed by Marriott Hotel. While eating the chicken she thought she was biting into a worm and got very upset by it and sued Marriott for half million dollars for breach of implied warranty, under UCC 2-314. Expert testified that the worm was probably a part of trachea or arota from the chicken's anatomy, which is very natural for fried chicken wings. The judge, however, denied summery judgment request by the defendant and permitted the case to go to jury.

I don't remember the outcome of that case but I suggest that you should talk a lawyer to find out more.