Roscoe leaves most of the spilled credit cards lying on the ground at the scene where the Dukes dumped them on his head, yet later when he and J.D. are looking through the satchel's contents, the big pile of cards are all there again.
The mercs conceal their bag of loot from the pursuing Cletus by tossing it behind a big log beside the road, yet from where the Dukes see it, the satchel is shown to be sitting out in the middle of a clear patch of bare ground, near a group of boulders and in plain sight of the road.
Roscoe leaves most of the credit cards lying at the side of the road when he hurries back to town with the satchel. No experienced/disciplined law-enforcement officer --- even a corrupt one --- would leave valuable evidence behind, especially when said evidence could be used to commit more crimes, like stolen credit cards certainly could by anyone who happened to stumble on the scatter pile of the remaining cards.