It was really hard to find this trap for the knowledge. I was just running there, "hugging" every tree (feeling me silly) and aiming up at those trees to hit trap on time before it disappears.
Did about 3 rounds at those locations till got it.

Look at the trees in the listed locations and you'll see the traps (See my screenshot) it basically looks like a very painful log swing. Once you can see it on your screen you only have a few seconds before it'll disappear (3-5 sec maximum). I used an AOE attack to break them quickly.