It is on the first disc about a quarter into the extended adition but also in the normal addition in the scene titled Riders of Rohan. After Legolas, Gimli, And Aaragorn get acqainted with the leader of the riders of Rohan, the leader says "Look for your friends but do not trust a hope. It is forsaken in these lands". A second before that look to the left of Aragorn's head and you will see the leader,s sword fall out of the scabbard. Look carefully, blink and you'll miss it.