2010 Tacoma engine problems

I have an 2010 toyota tacoma trd off road with a 4.0 v6, i purchased the truck earlier this year(June) with 10,800 miles on it, i just did the second oil chnge since i had it, first one at 14000, second at 18,000 miles. I use Mobil 1 5w-30 and Toyota Oil filters. When i was draining the oil this time i bearing material and metal (like a fine silt) were coming out of the pan, i have never drove the truck hard and it doesnt make any noises. I was just wondering if any one else has had this happen and how hard will i have to fight with the dealerrship to get it warrantied. Truck has 18,026 miles on it right now.