How did Huck and Jim spend their time on the raft?

In Chapter 12, Jim and Huck spend a few days traveling down the river. They improve the raft by building a wigwam, which will keep them dry and warm. Each night, Huck goes into a nearby town and buys more provisions for the next day. They only travel at night to avoid being seen and questioned.

One night, during a strong storm, they see a wrecked steamboat ahead of them. Huck convinces Jim to tie the raft to the boat and climb on board. They are surprised to hear voices, which Huck goes to investigate. There are three robbers on board, two of whom have tied up the third man. Apparently the bound man had threatened to turn them all in to the state. One of the robbers wants to kill him immediately, but the other man restrains him. The two men finally decide to kill their partner by leaving him on the boat and waiting until it sinks.

At this news, Huck scrambles back to rejoin Jim. Together they discover that their raft has come untied and floated away.