Re:Truffle

Question

I believe that truffles are mushrooms which can only grow in the wild. They cannot be planted or grown. Truffle farmers use pigs to locate the truffles in the ground. Thus, they are extremely expensive. I have heard that they are not kosher and I assume it is because the pigs are used to find them. Assuming all of this is true is there any possible way these truffles would not be kosher? Even if the mushrooms were touched by a pig they would still be kosher right?