Entry #13 was posted on September 10, 2009.
It has the description "I was close by".
In total, this clip is 1:29 long.
It is a clip of Alex asking Jay to get something from the car, then walking through the forest and eventually seeing the Operator near a building. Other than the title screen, there are no captions in this entry.
Main Theories and Observations
This was the first Entry to have text comments temporarily enabled, though Jay has confirmed this was an accident.
Speculation and Analysis
Alex seems to be seeking out The Operator in this clip. ~Morscata12
It is very possible that the cut in the video occurs because something was taken out—something like the video from the exit. ~Dav Flamerock
Slenderman can move unusually fast, maybe there is more than one? - Lifegospel
1 Here, Alex is referring to a camera battery, confirmed by J's twitter on September 17, 2009.