"FATAL ERROR: could not load world file" when trying to load my own custom story

[ferretpuke]

I'm new to this, so forgive me if I'm vague or otherwise unclear.
I was trying out the HPL2 level editor and made a few rooms, then decided I wanted to test one.
at first it wasn't showing up under the in-game custom story menu at all, but after a bunch of fiddling with files I got that fixed. the problem is that now when I choose to load my custom story, the game crashes and gives me an error message.
the full message looks like this:

FATAL ERROR

FATAL ERROR: Could not load world file '/Users/Matthew/Library/Application Support/Frictional Games/Amnesia/local_resources/custom_stories/awesome/maps/firstroom.map