Castle Grant was thought to have been snapped up last month less than a fortnight after going up for sale.
Selling agents revealed that an offer had been made by the first family to view the pile.
However, it is understood the sale has fallen through and the property, on the outskirts of Grantown-on-Spey, is now being advertised again for offers over £1.1 million.
Whyte bought the castle for £720,000 in 2006 with a 110 per cent mortgage but he fell into arrears with the £7,000-a-month mortgage payments.
The Bank of Scotland raised a legal action against him last year after he had failed to make the repayments from 2012.
The battle came to an end at Inverness Sheriff Court when the property was repossessed.
He sought help from his father Tom who supervised workmen as they cleared the castle of his belongings.
Last month, it was thought that a woman based in Aberdeen, who wished to remain anonymous, had made a successful offer for the castle within days of it going on sale.
Yesterday, Strutt and Parker confirmed the property was being advertised for sale again on its website.