In this case, its sounds like the appraiser was duped, but it is a scary thought. It makes for a good argument to get the sales contract on your transactions (besides other obvious reasons, like understanding the terms of the sale). We match up the seller with public record.
I am amazed how many real estate brokers have said to us that we are the first firm to actually ask for a copy of the contract.
Its a USPAP standard as part of the appraisal licensing requirement [i-2e(iv)]