If you were to look closer still, you would find some broken twigs. The crumbled leaves are from an older track. As you walk, your shoes pick up material from the ground. In this case, someone was walking on sand, then stepped on the piece of driftwood. The sand that was transferred left a pattern from their shoe.
Tracks can be anywhere.
If you step on a piece of paper, you leave a track on it. If you step on an aluminum can, you leave a mark on it. If you control the source of light, you can see these hidden tracks. In a dark room, hold a flashlight at a very low angle to the object you are examining. You should be able to see the dust transfer on the object.