Have you ever tried

• dropping things in the passageway?
• entering other compartments (they're all different!)
• photographing things at the train platform?
• photographing the bad spy? yourself? the camera?
• pulling the stop cord on the train?
• jumping out the window in your compartment?
• giving the document (or shreds) to the bad spy?
• reading the graffiti in the bathroom?
• putting things in the sink?
• flushing things down the toilet?
• trying to hide the document every place you can think of?
• taking a gun from one of the guards?
• having the bomb explode in the car? Or in or adjacent to the hut? Or the shed?
• going farther into the swamp?
• knocking on the tower door for a second time?
• using the binoculars? On something you're carrying?
• climbing the hut?
• buying food from the vendor?
• taking food after toppling the cart?
• throwing things at Topaz as he chases you?
• killing the sniper yourself? with Topaz's gun?
• figuring out how many Infocom people live in the Gribnitz apartments?