it’s been awhile since I read that story. But it does end abruptly. As I recall he has his scary experience once he gets through the cave the first time… then convinces himself he needs to go back one more time. This is where the story should end, presumably having met his doom on his last return trip. It is possible I also missed something, but this was how I took it.
I did a bit of, um, digging online and found that Ted’s Story is essentially a shortened, ‘Blair Witchified’ version of The Fear of Darkness, by Thomas Lera.
Lera’s story ends differently. You can read it here (warning: link points to a PDF).