The smugness and swagger in the animation of the people stealing your notes is great. Ditto for the animation of slenderman drawing a new note, you can feel the annoyance.
It's good that you have more than one enemy type, but some map variety probably would have helped too. When it's just a sparse forest, I can always see all the way to the next target.
If there was a building that I had to get around, a tunnel, an industrial park, or even just a change in elevation, then there could be more strategy in which notes to prioritize reposting.
Also, I like that the people are visible by their flashlights in the distance, but the pixelated camera filter seems counterproductive to that feature. Right now, you can't easily preemptively strike people before they get to the tree. If the field was darker and their flashlights were brighter, it could make you more proactive than having to wait for them to take your notes.