Case 002
The case
Champu Bandar robbed Sunrise Bank and escaped with a bag of money. Witnesses saw him running toward the river. When Detective Lomdi reached the riverbank, she found a trail of footprints in the sand. The footprints pointed directly toward a waiting boat. Meenu Murghi, the boat operator, said: "Champu never boarded my boat. I have been here all morning, and the boat is empty." Detective Lomdi carefully studied the footprints. She soon realized that Champu had never escaped across the river.
Your question
How did Detective Lomdi know Champu hadn't escaped across the river?