hard to get anything back

as most existing home sold "as is" with no guarantee. The buyer may have to accept if no defect found before closing.

One case is if you have evidence to show the seller phically know the defect and did not disclosed on seller disclosue. It can be treated frault.

Just based on what you stated may not be enough evidence to say the seller know the defect. If I am the seller, I will state that the carpet change company did not tell me anything when carpet changed.