20 YEARS TO TRACE DA VINCI AN FBI expert has warned a priceless masterpiece stolen from a Scots stately home may not surface for decades. The news came on the second anniversary of the theft of Leonardo Da Vinci's Madonna from Drumlanrig Castle,home to the Duke of Buccleuch. Madonna with the Yardwinder was stolen from the Dumfries castle by two thieves posing as tourists. The16th century painting is valued at up to �50million. FBI art theft expert Bob Wittam said: "We have seen material taken and only after about 20 years does it show up on the market again. "It may have been bought by an unsuspecting collector who didn't know it was stolen. "You then have it on the wall for years and when the collector dies, the heir decides to sell it