Build only on trigger. {"message":"No builds created"}

I am running Gitlab CE 8.13. I have a job that is defined to run only on trigger. I have created a trigger but I am struggling with this feature. I keep getting {“message”:“No builds created”} when I try to trigger it. What is supposed to go in the ref= portion of the trigger script? I have tried the word triggers and the word master. Maybe I have to create some special tag and ref that?

curl -X POST -F token=triggertokena89e1873ca75 -F ref=triggers
This is the relevent portion of my .gitlab-ci.yml.

  environment: production
  image: python:latest
  - my script here
  - triggers
- docker

I think I figured out the problem. I had some manual jobs and my triggered job was below them. I moved my trigger job up in my .gitlab-ci.yml file and it started working after that.