Were you under contract already? In other words, had you already completed the inspection negotiations and attorney review?
If so, it would be difficult for the seller to default without consent from all parties if all the contingencies had been removed. In fact, if this is the case, and you really want the home (and the hassle), you are in a position where you can bring a "specific performance lawsuit" to force the seller to complete the sale on the agreed-upon terms stipulated in the contract.
And because a contract is in place, your attorney could record a "lis pendens" against the title to ensure the seller does not attempt to sell to another buyer.
However, if this "seller's remorse" occured before the attorney review was completed and before conditions of the contract had been met, the seller can back out with no explanation, and you will get your earnest money deposit back.