What does Billie McCandless leave at the bus?

C. A suitcase stocked with survival supplies as well as a Bible

Billie and Walt wander in and out of the bus for the next two hours. Walt installs a memorial just inside the door, a simple brass plaque inscribed with a few words. Beneath it Billie arranges a bouquet of fireweed, monkshood, yarrow, and spruce boughs. Under the bed at the rear of the bus, she leaves a suitcase stocked with a first-aid kit, canned food, other survival supplies, a note urging whoever happens to read it to “call your parents as soon as possible.” The suitcase also holds a Bible that belonged to Chris when he was a child, even though, she allows, “I haven’t prayed since we lost him.”