AFAIK, at least in Russia there are signaling systems that will interpret a metal object connecting the rails as "another train is on the track" and inform the train driver.
Not sure whether those systems are also installed in the wilderness though. But it seems kinda likely that anybody thinking "I should derail a train for fun" might not bother driving into the wilderness when there's an alluring, convenient, seemingly unobserved stretch of the railway available nearby.
Edit: another thing that comes to mind is that you'd also have to find a low-visibility part of the railway, even in the wilderness — because otherwise the driver will just notice the obstacle and stop the train.
Not sure whether those systems are also installed in the wilderness though. But it seems kinda likely that anybody thinking "I should derail a train for fun" might not bother driving into the wilderness when there's an alluring, convenient, seemingly unobserved stretch of the railway available nearby.
Edit: another thing that comes to mind is that you'd also have to find a low-visibility part of the railway, even in the wilderness — because otherwise the driver will just notice the obstacle and stop the train.