Grammar

1. Bob Cole escaped from prison. The police checked all the airports and ports, but they weren't able to find him. Bob must not have left the country. Bob must have hidden somewhere. Bob might have had friends who helped him. He could have had a fake passport. He could have had a plan. 2. Jake robbed a bank, hijacked a plane and parachuted* over the Amazonian jungle. He's never been seen since. He must have been in the jungle. He might have been dead.** He could/might have expected some help. A bear might have killed him. He could not have completely disappeared.***

*or, parachuted out over ...

**or, He might have died. Although, your English is perfectly good, too.

***he did disappear, since no one found him, but he did not completely disappear (either his body or parts of his body remain, maybe? Or maybe not, if the bear ate him).

Very well written! I liked this mystery very much. What happened to Bob .... ?

Grammar

1. Bob Cole escaped from prison. The police checked all the airports and ports, but they weren't able to find him. Bob must not have left the country. Bob must have hidden in somewhere. Bob might have had friends who helped him. Bob could have had a fake passport. Bob could have had a plan. 2. Jake robbed a bank, hijacked a plane and parachuted out over the Amazon jungle. He's never been seen since. He must have been be in the jungle. He might have been be dead. He could have expected some help. A bear might have killed him. He could not have disappeared.

What I highlighted in blue is a little vague and sounds unnatural. You might what to use different wording here.

The last two corrections ("be in the jungle" and "be dead") were changed to present tense because Jake would still be in the jungle, and be dead, if these cases are true.