Good luck and best,
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If you employed a lawyer to handle the sale part of his due diligence was to establish whether the house was in the flood area. If he failed to do so then he was negligent.
As i said before most contracts in New Jersey include a clause that entitles you to search the official site of FEMA and establish whether the house is in the flood area.
Most towns maintain a map with the flood area delineated so a simple call to the town building dept would have resolved the question.
Not all Mls sites have the question about the flood area. If the mls in question did have the question on the listing and the listing agent did not declare the house was in the flood area then that agent has a problem.
Last but not least - yes get your earnest money back. Again if you have a lawyer that's his job
if you spent any money on inspections and appraisal you may be able to sue for that money back if they failed to disclose to you that it is in a flood zone